1. Introduction
1.1 What is .NET?
.NET is a general-purpose software development platform, similar to Java. At its core is a virtual machine that turns intermediate language (IL) into machine code. High-level language compilers for C#, VB.NET and C++ are provided to turn source code into IL. C# is a new programming language, very similar to Java. An extensive class library is included, featuring all the functionality one might expect from a contempory development platform - windows GUI development (Windows Forms), database access (ADO.NET), web development (ASP.NET), web services, XML etc.
See also Microsoft's definition.
1.2 When was .NET announced?
Bill Gates delivered a keynote at Forum 2000, held June 22, 2000, outlining the .NET 'vision'. The July 2000 PDC had a number of sessions on .NET technology, and delegates were given CDs containing a pre-release version of the .NET framework/SDK and Visual Studio.NET.
1.3 What versions of .NET are there?
The final versions of the 1.0 SDK and runtime were made publicly available around 6pm PST on 15-Jan-2002. At the same time, the final version of Visual Studio.NET was made available to MSDN subscribers.
.NET 1.1 was released in April 2003, and was mostly bug fixes for 1.0.
.NET 2.0 was released to MSDN subscribers in late October 2005, and was officially launched in early November.
1.4 What operating systems does the .NET Framework run on?
The runtime supports Windows Server 2003, Windows XP, Windows 2000, NT4 SP6a and Windows ME/98. Windows 95 is not supported. Some parts of the framework do not work on all platforms - for example, ASP.NET is only supported on XP and Windows 2000/2003. Windows 98/ME cannot be used for development.
IIS is not supported on Windows XP Home Edition, and so cannot be used to host ASP.NET. However, the ASP.NET Web Matrix web server does run on XP Home.
The .NET Compact Framework is a version of the .NET Framework for mobile devices, running Windows CE or Windows Mobile.
The Mono project has a version of the .NET Framework that runs on Linux.
1.5 What tools can I use to develop .NET applications?
There are a number of tools, described here in ascending order of cost:
The .NET Framework SDK is free and includes command-line compilers for C++, C#, and VB.NET and various other utilities to aid development.
SharpDevelop is a free IDE for C# and VB.NET.
Microsoft Visual Studio Express editions are cut-down versions of Visual Studio, for hobbyist or novice developers.There are different versions for C#, VB, web development etc. Originally the plan was to charge $49, but MS has decided to offer them as free downloads instead, at least until November 2006.
Microsoft Visual Studio Standard 2005 is around $300, or $200 for the upgrade.
Microsoft VIsual Studio Professional 2005 is around $800, or $550 for the upgrade.
At the top end of the price range are the Microsoft Visual Studio Team Edition for Software Developers 2005 with MSDN Premium and Team Suite editions.
You can see the differences between the various Visual Studio versions here.
1.6 Why did they call it .NET?
I don't know what they were thinking. They certainly weren't thinking of people using search tools. It's meaningless marketing nonsense.
2. Terminology
2.1 What is the CLI? Is it the same as the CLR?
The CLI (Common Language Infrastructure) is the definiton of the fundamentals of the .NET framework - the Common Type System (CTS), metadata, the Virtual Execution Environment (VES) and its use of intermediate language (IL), and the support of multiple programming languages via the Common Language Specification (CLS). The CLI is documented through ECMA - see http://msdn.microsoft.com/net/ecma/ for more details.
The CLR (Common Language Runtime) is Microsoft's primary implementation of the CLI. Microsoft also have a shared source implementation known as ROTOR, for educational purposes, as well as the .NET Compact Framework for mobile devices. Non-Microsoft CLI implementations include Mono and DotGNU Portable.NET.
2.2 What is the CTS, and how does it relate to the CLS?
CTS = Common Type System. This is the full range of types that the .NET runtime understands. Not all .NET languages support all the types in the CTS.
CLS = Common Language Specification. This is a subset of the CTS which all .NET languages are expected to support. The idea is that any program which uses CLS-compliant types can interoperate with any .NET program written in any language. This interop is very fine-grained - for example a VB.NET class can inherit from a C# class.
2.3 What is IL?
IL = Intermediate Language. Also known as MSIL (Microsoft Intermediate Language) or CIL (Common Intermediate Language). All .NET source code (of any language) is compiled to IL during development. The IL is then converted to machine code at the point where the software is installed, or (more commonly) at run-time by a Just-In-Time (JIT) compiler.
2.4 What is C#?
C# is a new language designed by Microsoft to work with the .NET framework. In their "Introduction to C#" whitepaper, Microsoft describe C# as follows:
"C# is a simple, modern, object oriented, and type-safe programming language derived from C and C++. C# (pronounced “C sharp”) is firmly planted in the C and C++ family tree of languages, and will immediately be familiar to C and C++ programmers. C# aims to combine the high productivity of Visual Basic and the raw power of C++."
Substitute 'Java' for 'C#' in the quote above, and you'll see that the statement still works pretty well :-).
If you are a C++ programmer, you might like to check out my C# FAQ.
2.5 What does 'managed' mean in the .NET context?
The term 'managed' is the cause of much confusion. It is used in various places within .NET, meaning slightly different things.
Managed code: The .NET framework provides several core run-time services to the programs that run within it - for example exception handling and security. For these services to work, the code must provide a minimum level of information to the runtime. Such code is called managed code.
Managed data: This is data that is allocated and freed by the .NET runtime's garbage collector.
Managed classes: This is usually referred to in the context of Managed Extensions (ME) for C++. When using ME C++, a class can be marked with the __gc keyword. As the name suggests, this means that the memory for instances of the class is managed by the garbage collector, but it also means more than that. The class becomes a fully paid-up member of the .NET community with the benefits and restrictions that brings. An example of a benefit is proper interop with classes written in other languages - for example, a managed C++ class can inherit from a VB class. An example of a restriction is that a managed class can only inherit from one base class.
2.6 What is reflection?
All .NET compilers produce metadata about the types defined in the modules they produce. This metadata is packaged along with the module (modules in turn are packaged together in assemblies), and can be accessed by a mechanism called reflection. The System.Reflection namespace contains classes that can be used to interrogate the types for a module/assembly.
Using reflection to access .NET metadata is very similar to using ITypeLib/ITypeInfo to access type library data in COM, and it is used for similar purposes - e.g. determining data type sizes for marshaling data across context/process/machine boundaries.
Reflection can also be used to dynamically invoke methods (see System.Type.InvokeMember), or even create types dynamically at run-time (see System.Reflection.Emit.TypeBuilder).
3.1 What is an assembly?
An assembly is sometimes described as a logical .EXE or .DLL, and can be an application (with a main entry point) or a library. An assembly consists of one or more files (dlls, exes, html files etc), and represents a group of resources, type definitions, and implementations of those types. An assembly may also contain references to other assemblies. These resources, types and references are described in a block of data called a manifest. The manifest is part of the assembly, thus making the assembly self-describing.
An important aspect of assemblies is that they are part of the identity of a type. The identity of a type is the assembly that houses it combined with the type name. This means, for example, that if assembly A exports a type called T, and assembly B exports a type called T, the .NET runtime sees these as two completely different types. Furthermore, don't get confused between assemblies and namespaces - namespaces are merely a hierarchical way of organising type names. To the runtime, type names are type names, regardless of whether namespaces are used to organise the names. It's the assembly plus the typename (regardless of whether the type name belongs to a namespace) that uniquely indentifies a type to the runtime.
Assemblies are also important in .NET with respect to security - many of the security restrictions are enforced at the assembly boundary.
Finally, assemblies are the unit of versioning in .NET - more on this below.
3.2 How can I produce an assembly?
The simplest way to produce an assembly is directly from a .NET compiler. For example, the following C# program:
public class CTest
{
public CTest() { System.Console.WriteLine( "Hello from CTest" ); }
}
can be compiled into a library assembly (dll) like this:
csc /t:library ctest.cs
You can then view the contents of the assembly by running the "IL Disassembler" tool that comes with the .NET SDK.
Alternatively you can compile your source into modules, and then combine the modules into an assembly using the assembly linker (al.exe). For the C# compiler, the /target:module switch is used to generate a module instead of an assembly.
3.3 What is the difference between a private assembly and a shared assembly?
Location and visibility: A private assembly is normally used by a single application, and is stored in the application's directory, or a sub-directory beneath. A shared assembly is normally stored in the global assembly cache, which is a repository of assemblies maintained by the .NET runtime. Shared assemblies are usually libraries of code which many applications will find useful, e.g. the .NET framework classes.
Versioning: The runtime enforces versioning constraints only on shared assemblies, not on private assemblies.
3.4 How do assemblies find each other?
By searching directory paths. There are several factors which can affect the path (such as the AppDomain host, and application configuration files), but for private assemblies the search path is normally the application's directory and its sub-directories. For shared assemblies, the search path is normally same as the private assembly path plus the shared assembly cache.
3.5 How does assembly versioning work?
Each assembly has a version number called the compatibility version. Also each reference to an assembly (from another assembly) includes both the name and version of the referenced assembly.
The version number has four numeric parts (e.g. 5.5.2.33). Assemblies with either of the first two parts different are normally viewed as incompatible. If the first two parts are the same, but the third is different, the assemblies are deemed as 'maybe compatible'. If only the fourth part is different, the assemblies are deemed compatible. However, this is just the default guideline - it is the version policy that decides to what extent these rules are enforced. The version policy can be specified via the application configuration file.
Remember: versioning is only applied to shared assemblies, not private assemblies.
3.6 How can I develop an application that automatically updates itself from the web?
For .NET 1.x, use the Updater Application Block. For .NET 2.x, use ClickOnce.
4. Application Domains
4.1 What is an application domain?
An AppDomain can be thought of as a lightweight process. Multiple AppDomains can exist inside a Win32 process. The primary purpose of the AppDomain is to isolate applications from each other, and so it is particularly useful in hosting scenarios such as ASP.NET. An AppDomain can be destroyed by the host without affecting other AppDomains in the process.
Win32 processes provide isolation by having distinct memory address spaces. This is effective, but expensive. The .NET runtime enforces AppDomain isolation by keeping control over the use of memory - all memory in the AppDomain is managed by the .NET runtime, so the runtime can ensure that AppDomains do not access each other's memory.
One non-obvious use of AppDomains is for unloading types. Currently the only way to unload a .NET type is to destroy the AppDomain it is loaded into. This is particularly useful if you create and destroy types on-the-fly via reflection.
Microsoft have an AppDomain FAQ.
4.2 How does an AppDomain get created?
AppDomains are usually created by hosts. Examples of hosts are the Windows Shell, ASP.NET and IE. When you run a .NET application from the command-line, the host is the Shell. The Shell creates a new AppDomain for every application.
AppDomains can also be explicitly created by .NET applications. Here is a C# sample which creates an AppDomain, creates an instance of an object inside it, and then executes one of the object's methods:
using System;
using System.Runtime.Remoting;
using System.Reflection;
public class CAppDomainInfo : MarshalByRefObject
{
public string GetName() { return AppDomain.CurrentDomain.FriendlyName; }
}
public class App
{
public static int Main()
{
AppDomain ad = AppDomain.CreateDomain( "Andy's new domain" );
CAppDomainInfo adInfo = (CAppDomainInfo)ad.CreateInstanceAndUnwrap(
Assembly.GetCallingAssembly().GetName().Name, "CAppDomainInfo" );
Console.WriteLine( "Created AppDomain name = " + adInfo.GetName() );
return 0;
}
}
4.3 Can I write my own .NET host?
Yes. For an example of how to do this, take a look at the source for the dm.net moniker developed by Jason Whittington and Don Box. There is also a code sample in the .NET SDK called CorHost.
Sunday, June 29, 2008
Unix Basics
Basic UNIX commands
Note: not all of these are actually part of UNIX itself, and you may not find them on all UNIX machines. But they can all be used on turing in essentially the same way, by typing the command and hitting return. Note that some of these commands are different on non-Solaris machines - see SunOS differences.
If you've made a typo, the easiest thing to do is hit CTRL-u to cancel the whole line. But you can also edit the command line (see the guide to More UNIX).
UNIX is case-sensitive.
Files
• ls --- lists your files
ls -l --- lists your files in 'long format', which contains lots of useful information, e.g. the exact size of the file, who owns the file and who has the right to look at it, and when it was last modified.
ls -a --- lists all files, including the ones whose filenames begin in a dot, which you do not always want to see.
There are many more options, for example to list files by size, by date, recursively etc.
• more filename --- shows the first part of a file, just as much as will fit on one screen. Just hit the space bar to see more or q to quit. You can use /pattern to search for a pattern.
• emacs filename --- is an editor that lets you create and edit a file. See the emacs page.
• mv filename1 filename2 --- moves a file (i.e. gives it a different name, or moves it into a different directory (see below)
• cp filename1 filename2 --- copies a file
• rm filename --- removes a file. It is wise to use the option rm -i, which will ask you for confirmation before actually deleting anything. You can make this your default by making an alias in your .cshrc file.
• diff filename1 filename2 --- compares files, and shows where they differ
• wc filename --- tells you how many lines, words, and characters there are in a file
• chmod options filename --- lets you change the read, write, and execute permissions on your files. The default is that only you can look at them and change them, but you may sometimes want to change these permissions. For example, chmod o+r filename will make the file readable for everyone, and chmod o-r filename will make it unreadable for others again. Note that for someone to be able to actually look at the file the directories it is in need to be at least executable. See help protection for more details.
• File Compression
o gzip filename --- compresses files, so that they take up much less space. Usually text files compress to about half their original size, but it depends very much on the size of the file and the nature of the contents. There are other tools for this purpose, too (e.g. compress), but gzip usually gives the highest compression rate. Gzip produces files with the ending '.gz' appended to the original filename.
o gunzip filename --- uncompresses files compressed by gzip.
o gzcat filename --- lets you look at a gzipped file without actually having to gunzip it (same as gunzip -c). You can even print it directly, using gzcat filename | lpr
• printing
o lpr filename --- print. Use the -P option to specify the printer name if you want to use a printer other than your default printer. For example, if you want to print double-sided, use 'lpr -Pvalkyr-d', or if you're at CSLI, you may want to use 'lpr -Pcord115-d'. See 'help printers' for more information about printers and their locations.
o lpq --- check out the printer queue, e.g. to get the number needed for removal, or to see how many other files will be printed before yours will come out
o lprm jobnumber --- remove something from the printer queue. You can find the job number by using lpq. Theoretically you also have to specify a printer name, but this isn't necessary as long as you use your default printer in the department.
o genscript --- converts plain text files into postscript for printing, and gives you some options for formatting. Consider making an alias like alias ecop 'genscript -2 -r \!* | lpr -h -Pvalkyr' to print two pages on one piece of paper.
o dvips filename --- print .dvi files (i.e. files produced by LaTeX). You can use dviselect to print only selected pages. See the LaTeX page for more information about how to save paper when printing drafts.
Directories
Directories, like folders on a Macintosh, are used to group files together in a hierarchical structure.
• mkdir dirname --- make a new directory
• cd dirname --- change directory. You basically 'go' to another directory, and you will see the files in that directory when you do 'ls'. You always start out in your 'home directory', and you can get back there by typing 'cd' without arguments. 'cd ..' will get you one level up from your current position. You don't have to walk along step by step - you can make big leaps or avoid walking around by specifying pathnames.
• pwd --- tells you where you currently are.
Finding things
• ff --- find files anywhere on the system. This can be extremely useful if you've forgotten in which directory you put a file, but do remember the name. In fact, if you use ff -p you don't even need the full name, just the beginning. This can also be useful for finding other things on the system, e.g. documentation.
• grep string filename(s) --- looks for the string in the files. This can be useful a lot of purposes, e.g. finding the right file among many, figuring out which is the right version of something, and even doing serious corpus work. grep comes in several varieties (grep, egrep, and fgrep) and has a lot of very flexible options. Check out the man pages if this sounds good to you.
About other people
• w --- tells you who's logged in, and what they're doing. Especially useful: the 'idle' part. This allows you to see whether they're actually sitting there typing away at their keyboards right at the moment.
• who --- tells you who's logged on, and where they're coming from. Useful if you're looking for someone who's actually physically in the same building as you, or in some other particular location.
• finger username --- gives you lots of information about that user, e.g. when they last read their mail and whether they're logged in. Often people put other practical information, such as phone numbers and addresses, in a file called .plan. This information is also displayed by 'finger'.
• last -1 username --- tells you when the user last logged on and off and from where. Without any options, last will give you a list of everyone's logins.
• talk username --- lets you have a (typed) conversation with another user
• write username --- lets you exchange one-line messages with another user
• elm --- lets you send e-mail messages to people around the world (and, of course, read them). It's not the only mailer you can use, but the one we recommend. See the elm page, and find out about the departmental mailing lists (which you can also find in /user/linguistics/helpfile).
About your (electronic) self
• whoami --- returns your username. Sounds useless, but isn't. You may need to find out who it is who forgot to log out somewhere, and make sure *you* have logged out.
• finger & .plan files
of course you can finger yourself, too. That can be useful e.g. as a quick check whether you got new mail. Try to create a useful .plan file soon. Look at other people's .plan files for ideas. The file needs to be readable for everyone in order to be visible through 'finger'. Do 'chmod a+r .plan' if necessary. You should realize that this information is accessible from anywhere in the world, not just to other people on turing.
• passwd --- lets you change your password, which you should do regularly (at least once a year). See the LRB guide and/or look at help password.
• ps -u yourusername --- lists your processes. Contains lots of information about them, including the process ID, which you need if you have to kill a process. Normally, when you have been kicked out of a dialin session or have otherwise managed to get yourself disconnected abruptly, this list will contain the processes you need to kill. Those may include the shell (tcsh or whatever you're using), and anything you were running, for example emacs or elm. Be careful not to kill your current shell - the one with the number closer to the one of the ps command you're currently running. But if it happens, don't panic. Just try again :) If you're using an X-display you may have to kill some X processes before you can start them again. These will show only when you use ps -efl, because they're root processes.
• kill PID --- kills (ends) the processes with the ID you gave. This works only for your own processes, of course. Get the ID by using ps. If the process doesn't 'die' properly, use the option -9. But attempt without that option first, because it doesn't give the process a chance to finish possibly important business before dying. You may need to kill processes for example if your modem connection was interrupted and you didn't get logged out properly, which sometimes happens.
• quota -v --- show what your disk quota is (i.e. how much space you have to store files), how much you're actually using, and in case you've exceeded your quota (which you'll be given an automatic warning about by the system) how much time you have left to sort them out (by deleting or gzipping some, or moving them to your own computer).
• du filename --- shows the disk usage of the files and directories in filename (without argument the current directory is used). du -s gives only a total.
• last yourusername --- lists your last logins. Can be a useful memory aid for when you were where, how long you've been working for, and keeping track of your phonebill if you're making a non-local phonecall for dialling in.
Connecting to the outside world
• nn --- allows you to read news. It will first let you read the news local to turing, and then the remote news. If you want to read only the local or remote news, you can use nnl or nnr, respectively. To learn more about nn type nn, then \tty{:man}, then \tty{=.*}, then \tty{Z}, then hit the space bar to step through the manual. Or look at the man page. Or check out the hypertext nn FAQ - probably the easiest and most fun way to go.
• rlogin hostname --- lets you connect to a remote host
• telnet hostname --- also lets you connect to a remote host. Use rlogin whenever possible.
• ftp hostname --- lets you download files from a remote host which is set up as an ftp-server. This is a common method for exchanging academic papers and drafts. If you need to make a paper of yours available in this way, you can (temporarily) put a copy in /user/ftp/pub/TMP. For more permanent solutions, ask Emma. The most important commands within ftp are get for getting files from the remote machine, and put for putting them there (mget and mput let you specify more than one file at once). Sounds straightforward, but be sure not to confuse the two, especially when your physical location doesn't correspond to the direction of the ftp connection you're making. ftp just overwrites files with the same filename. If you're transferring anything other than ASCII text, use binary mode.
• lynx --- lets you browse the web from an ordinary terminal. Of course you can see only the text, not the pictures. You can type any URL as an argument to the G command. When you're doing this from any Stanford host you can leave out the .stanford.edu part of the URL when connecting to Stanford URLs. Type H at any time to learn more about lynx, and Q to exit.
Miscellaneous tools
• webster word --- looks up the word in an electronic version of Webster's dictionary and returns the definition(s)
• date --- shows the current date and time.
• cal --- shows a calendar of the current month. Use e.g., 'cal 10 1995' to get that for October 95, or 'cal 1995' to get the whole year.
password
When you received your username and password from the consulting desk, the password was a generated password. You should personalize your own password so that it is easy to remember without being something others could easily guess. It should not be a word that is in a dictionary (as a program can be written to try all the words in a dictionary in seconds). Your password has to be at least 6 characters. It can be letters (UPPER case or lower case) or numbers. CHANGE IT!
DO NOT give your password to others. This is an account and you are responsible for what is done on this account. If you give the password to someone else and they do something wrong, your account information will be pointing to you. DO NOT give your password to others.
If or when you change your password, it might take a few minutes for the new password to be activated. There are several changes that must take place on several computers. Be patient. If you just changed your password and the new password doesn't work yet, the old password is still active and it will work.
type this in this is what it will do
sunburst% password you will be prompted to enter your old password
old password enter your old password here
new password you will be asked to enter a new password
new password type it again for verification
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ls (list schema)
The ls command displays the files and directories in your current working directory. If there are no visible files in your directory, the UNIX prompt will be returned. ls does not display hidden files which begin with a . (period). To display all files you must include the option -a.
type this in this is what it will do
sunburst% ls displays the files and directories in your current directory
sunburst% ls -a displays all files and directories (even the hidden ones)
sunburst% ls -l displays all files and directories w/FULL description
sunburst% dir same as ls -l (alias for DOS people)
sunburst% ls -R displays all files and directories in current directory and below (recursive)
You should not delete or change any hidden files. These files are created for administrative use of your e-mail, news readers, login, etc.
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mkdir (make directory)
The mkdir command will create a subdirectory inside of your current working directory. If you are logged into sunburst go ahead and try the command as follows.
type this in this is what will happen
sunburst% mkdir tutor_stuff this will create a subdirectory called tutor_stuff
Now let us look to make sure the directory was actually created.
sunburst% ls should display your files and subdirectories in your current working directory (including the subdirectory you just created.)
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cd (change directories)
The cd command will change the current working directory to the location or path you type.
sunburst% cd tutor_stuff change the working directory to tutor_stuff
sunburst% cd .. cd followed by .. will take you to the current parent directory
sunburst% cd cd by itself will take you to your home directory
no matter where you currently are
sunburst% cd tutor_stuff change the working directory to tutor_stuff
If you type in the ls command here (make sure you are inside of tutor_stuff) you should see that the directory (you just created) is empty. Try it and see! Now that you are in the directory called tutor_stuff create another subdirectory called more_stuff. We will use this subdirectory later.
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touch (touches a file and updates it)
The touch command will update the last time a file was edited. If you touch a file that doesn't yet exist, it will create a file with zero length. You probably won't use it much, but it will allow us to easily create files that we will use and delete later.
sunburst% cd ~/tutor_stuff makes sure everyone is in the right place
sunburst% touch testfile creates a file named testfile
sunburst% ls check to see if the file is there
Create another file of your own choice. Make sure you remember the name so you can delete it later.
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pwd (print working directory)
The pwd command shows you where you are (path wise) on the computer (server - not your desktop). You have probably noticed that every time you change directories you get a description of the path. Sometimes it is necessary to know your current path without changing to a different directory.
sunburst% cd takes you to your home directory
sunburst% pwd prints your working directory
you should see something like /home/coyote/username
sunburst% cd tutor_stuff takes you to tutor_stuff subdirectory
sunburst% pwd you should see /home/coyote/username/tutor_stuff
See if you can get back to the more_stuff subdirectory. Next, have the full pathname printed to the screen using the pwd command. (Can you guess what the full pathname will be?)
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Miscellaneous stuff about directories and pathnames
Follow the directions and make sure you understand what is happening.
sunburst% cd takes you to your home directory
sunburst% ls lists files and directories in the current directory
sunburst% ls tutor_stuff lists files and directories inside of tutor_stuff
sunburst% ls what is not a directory and will say "what not found"
sunburst% ls ~ lists files and directories in your home directory
(no matter where you currently are in the system)
The tilde (~) is a reference to your home directory.
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cp (copy file)
You can make an exact copy of a file using the copy (cp) command.
sunburst% cd ~/tutor_stuff makes sure everyone is in the right place
sunburst% cp testfile file2 makes a copy of testfile and calls it file2
sunburst% dir make sure the files are really there
See if you can make a copy of file2 (call it file3).
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mv (move file)
The mv command moves files and directories around in the file system. You can also use the mv command to rename a file. To make sure these examples work you must be inside of tutor_stuff with the testfile and file2 created.
sunburst% mv testfile file1 renames testfile with the name of file1
sunburst% mv file1 .. moves file1 to its parent directory
sunburst% mv file2 more_stuff moves file2 into subdirectory more_stuff
See if you can move the file2 that is in more_stuff back to tutor_stuff. Also move the file1 that is in home directory back to tutor_stuff. If you do this you should have file1, file2, and file3 inside of tutor_stuff. Use the dir or ls commands to make sure you moved the files to the right spots.
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rm (remove file)
The rm command removes or deletes files from the file system. You must be careful. DO NOT delete anything you might need later. You can't get it back.
sunburst% rm file1 removes file1
sunburst% rm file3 .. removes file3
Check to see that file2 still exists and that file1 and file3 are gone. Then remove file2.
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rmdir (remove directory)
The rmdir command will remove an empty directory. If you have followed closely up to this point you should not have any files in the subdirectory more_stuff, so let's remove that directory.
sunburst% cd ~/tutor_stuff makes sure everyone is in the right place
sunburst% rmdir more_stuff removes directory called more_stuff
See if you can remove the directory tutor_stuff. You need to make sure that there are no files or directories inside. (Remember you created another file of your choice - with a touch command earlier.)
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chmod (changing a file mode)
The chmod command lets the owner of a file change the permissions settings for a file or directory. These permissions are displayed with the dir or ls -l listings. The permissions are in the form of
-rwxrwxrwx
This collection of letters tells us how the permissions for a file (starting with a -) or directory (starting with a d) are set. The first three letters give the permissions for the owner of the file. The middle group (next three letters) give us the permissions for the group to which the owner belongs. The last three letters tell the permissions for everyone else. The permissions can be set for directories as well as files but have slightly different meanings.
files
• r- read permission
• w-write permission
• x-execute permission
directories
• r-permission to list files in a directory
• w-permission to delete files or move files
• x-permission to access to files in the directory
permissions
owner group everyone
- rwx rwx rwx
codes r - Read Permission
4
w- Write Permission 2
x- Execute Permission
If you wanted to set a file with full permissions for yourself or owner (4+2+1)=7, read and write permissions for the group (4+2)=6 and read only for everyone 4=4, the command would be
chmod 764 filename.
Depending on what you are doing with (and from) the files, the permissions need to be set appropriately for owner, group and everyone.
________________________________________
du (disk utility)
The du command prints the number of kilobytes you have in each subdirectory. This can be useful to see which directory has the most files if you have gone over quota. From your home directory type
sunburst% du
________________________________________
quota (displays user quota and usage)
Each user on sunburst is allocated a certain amount of disk space (usually about 5 megabytes). If you exceed this quota some of your files must be removed within a certain time period. To check your quota and see how much you are using type
sunburst% quota -v
________________________________________
clear (clears screen)
The command clear just clears your terminal screen. Go ahead and try this. You should see a clear terminal window with sunburst% at the top.
________________________________________
Ways to display file contents
In order for us to experiment with the next five commands, we need to create an example file. To do this you can either type the list below exactly as it appears or you can highlight (or select) the list below and cut-n-paste it into UNIX at the sunburst% prompt. Either way will work the same. In this example we are sending the input from the keyboard into the file demofile. AFTER the list is either typed into UNIX or pasted from Netscape into UNIX you must stop the input with a return and a control-d.
---------------------------list below
cat > demofile
one
two
three
four
five
six
seven
eight
nine
ten
eleven
twelve
thirteen
fourteen
fifteen
sixteen
seventeen
eighteen
nineteen
twenty
twenty-one
twenty-two
twenty-three
twenty-four
twenty-five
twenty-six
------------------list above
AFTER the list is either typed into UNIX or pasted from Netscape into UNIX you must stop the input with a return and a control-d.
________________________________________
cat (concatenate)
The cat command will display the entire contents of the file on the terminal screen. If it is more than one page it will all scroll by quickly.
sunburst% cat demofile displays entire file contents to terminal screen
________________________________________
more (display one screen at a time)
To display the entire file one screen at a time use the more command instead of cat. After each screen is drawn you must hit the space bar to go on to the next screen.
sunburst% more demofile displays the file example one screen at a time
________________________________________
head (display first 10 lines of a file)
The head command will display the first 10 lines of a file.
sunburst% head demofile should display one - ten in our demofile
________________________________________
tail (displays last 10 lines of a file)
displays last 10 lines of a file
sunburst% tail demofile should display seventeen-twenty-six in our file
________________________________________
wc (word count)
The wc command will tell you how many lines, words and characters.
sunburst% wc demofile would return 26 lines 26 words and about 170 letters
If you pasted the info from Netscape there would be a few more letters because of additional spaces used in formatting HTML (approximately 383 letters).
________________________________________
* (wild card - matches none or more )
The * is a wild card that will replace anything in its place. Below are some examples of its use.
sunburst% dir *.gif displays all files ending with .gif
sunburst% dir test* displays all files beginning with test
________________________________________
? (wild card - matches just one character)
The ? is a wild card that will match one character only. Below is an examples of its use.
sunburst% dir test?.gif displays all files starting with test
then valid character
then ending with .gif
would not find test10.gif
________________________________________
file name conventions
Unix file names should contain only letters, numbers, underscore and period (. often referred to as dot). The file names can contain up to 256 characters. Try to give your file names meaning. Don't use all 256 characters.
Directories are basically a special type of file, so the rules for naming files apply to directories also.
________________________________________
!!
This is called the bang bang command. It will repeat the last command entered into unix from your keyboard. This is like the F3 command from DOS.
Try it!
A variation of this is ! followed by a letter (or letters). This will re-issue the last unix command that started with that letter (or letters). Lets look at the following example:
sunburst% dir would display the current working directory
sunburst% !! would repeat last command
sunburst% mkdir stuff creates directory stuff
sunburst% clear clears the terminal window
sunburst% cd stuff change working directory to stuff
sunburst% !c would try to change directories again
this wouldn't work because you are already there
sunburst% !cl would send the last unix command starting with cl which would be clear
________________________________________
More help directly from UNIX here
________________________________________
man
Read the UNIX on line manual page for a specific command.
sunburst% man cp displays online manual for copy command
Notice the --More--(26%) message at the bottom of the screen (if you type the above command). If you do not want to view the remaining pages you can [interrupt Process] with the Control-C command.
________________________________________
whatis
The whatis command will display a one-line explanation of a command.
sunburst% whatis cp displays a one-line description of the cp command
________________________________________
apropos
If you don't remember the UNIX command but you know you want to copy a file you can use the apropos command to find reference to the copy command within the online manual.
sunburst% apropos copy displays references to copy within the online manuals
________________________________________
A little fun?
________________________________________
finger
If you want to find out some information about another user (such as: are they logged on, when did they read their mail last, do they have a plan) you can use the finger command. The finger command reads some of those invisible files in your directory we were talking about earlier to display the information you will see on your screen.
sunburst% finger username@host displays information regarding the person you are checking on
________________________________________
talk
If you fingered someone and know that they are currently logged into sunburst you can talk to them. The talk command will split your window into a upper portion and lower portion. You will type on one and read the person's responses an the other port ion. It is kind of like a telephone (well no sound). You can do this with anyone in the world that is logged on if you know their e-mail address.
After you issue the talk command the other person should see a message that says you are requesting to talk to them. If they want to talk to you they need to type in a corresponding message on their computer screen.
Note: not all of these are actually part of UNIX itself, and you may not find them on all UNIX machines. But they can all be used on turing in essentially the same way, by typing the command and hitting return. Note that some of these commands are different on non-Solaris machines - see SunOS differences.
If you've made a typo, the easiest thing to do is hit CTRL-u to cancel the whole line. But you can also edit the command line (see the guide to More UNIX).
UNIX is case-sensitive.
Files
• ls --- lists your files
ls -l --- lists your files in 'long format', which contains lots of useful information, e.g. the exact size of the file, who owns the file and who has the right to look at it, and when it was last modified.
ls -a --- lists all files, including the ones whose filenames begin in a dot, which you do not always want to see.
There are many more options, for example to list files by size, by date, recursively etc.
• more filename --- shows the first part of a file, just as much as will fit on one screen. Just hit the space bar to see more or q to quit. You can use /pattern to search for a pattern.
• emacs filename --- is an editor that lets you create and edit a file. See the emacs page.
• mv filename1 filename2 --- moves a file (i.e. gives it a different name, or moves it into a different directory (see below)
• cp filename1 filename2 --- copies a file
• rm filename --- removes a file. It is wise to use the option rm -i, which will ask you for confirmation before actually deleting anything. You can make this your default by making an alias in your .cshrc file.
• diff filename1 filename2 --- compares files, and shows where they differ
• wc filename --- tells you how many lines, words, and characters there are in a file
• chmod options filename --- lets you change the read, write, and execute permissions on your files. The default is that only you can look at them and change them, but you may sometimes want to change these permissions. For example, chmod o+r filename will make the file readable for everyone, and chmod o-r filename will make it unreadable for others again. Note that for someone to be able to actually look at the file the directories it is in need to be at least executable. See help protection for more details.
• File Compression
o gzip filename --- compresses files, so that they take up much less space. Usually text files compress to about half their original size, but it depends very much on the size of the file and the nature of the contents. There are other tools for this purpose, too (e.g. compress), but gzip usually gives the highest compression rate. Gzip produces files with the ending '.gz' appended to the original filename.
o gunzip filename --- uncompresses files compressed by gzip.
o gzcat filename --- lets you look at a gzipped file without actually having to gunzip it (same as gunzip -c). You can even print it directly, using gzcat filename | lpr
• printing
o lpr filename --- print. Use the -P option to specify the printer name if you want to use a printer other than your default printer. For example, if you want to print double-sided, use 'lpr -Pvalkyr-d', or if you're at CSLI, you may want to use 'lpr -Pcord115-d'. See 'help printers' for more information about printers and their locations.
o lpq --- check out the printer queue, e.g. to get the number needed for removal, or to see how many other files will be printed before yours will come out
o lprm jobnumber --- remove something from the printer queue. You can find the job number by using lpq. Theoretically you also have to specify a printer name, but this isn't necessary as long as you use your default printer in the department.
o genscript --- converts plain text files into postscript for printing, and gives you some options for formatting. Consider making an alias like alias ecop 'genscript -2 -r \!* | lpr -h -Pvalkyr' to print two pages on one piece of paper.
o dvips filename --- print .dvi files (i.e. files produced by LaTeX). You can use dviselect to print only selected pages. See the LaTeX page for more information about how to save paper when printing drafts.
Directories
Directories, like folders on a Macintosh, are used to group files together in a hierarchical structure.
• mkdir dirname --- make a new directory
• cd dirname --- change directory. You basically 'go' to another directory, and you will see the files in that directory when you do 'ls'. You always start out in your 'home directory', and you can get back there by typing 'cd' without arguments. 'cd ..' will get you one level up from your current position. You don't have to walk along step by step - you can make big leaps or avoid walking around by specifying pathnames.
• pwd --- tells you where you currently are.
Finding things
• ff --- find files anywhere on the system. This can be extremely useful if you've forgotten in which directory you put a file, but do remember the name. In fact, if you use ff -p you don't even need the full name, just the beginning. This can also be useful for finding other things on the system, e.g. documentation.
• grep string filename(s) --- looks for the string in the files. This can be useful a lot of purposes, e.g. finding the right file among many, figuring out which is the right version of something, and even doing serious corpus work. grep comes in several varieties (grep, egrep, and fgrep) and has a lot of very flexible options. Check out the man pages if this sounds good to you.
About other people
• w --- tells you who's logged in, and what they're doing. Especially useful: the 'idle' part. This allows you to see whether they're actually sitting there typing away at their keyboards right at the moment.
• who --- tells you who's logged on, and where they're coming from. Useful if you're looking for someone who's actually physically in the same building as you, or in some other particular location.
• finger username --- gives you lots of information about that user, e.g. when they last read their mail and whether they're logged in. Often people put other practical information, such as phone numbers and addresses, in a file called .plan. This information is also displayed by 'finger'.
• last -1 username --- tells you when the user last logged on and off and from where. Without any options, last will give you a list of everyone's logins.
• talk username --- lets you have a (typed) conversation with another user
• write username --- lets you exchange one-line messages with another user
• elm --- lets you send e-mail messages to people around the world (and, of course, read them). It's not the only mailer you can use, but the one we recommend. See the elm page, and find out about the departmental mailing lists (which you can also find in /user/linguistics/helpfile).
About your (electronic) self
• whoami --- returns your username. Sounds useless, but isn't. You may need to find out who it is who forgot to log out somewhere, and make sure *you* have logged out.
• finger & .plan files
of course you can finger yourself, too. That can be useful e.g. as a quick check whether you got new mail. Try to create a useful .plan file soon. Look at other people's .plan files for ideas. The file needs to be readable for everyone in order to be visible through 'finger'. Do 'chmod a+r .plan' if necessary. You should realize that this information is accessible from anywhere in the world, not just to other people on turing.
• passwd --- lets you change your password, which you should do regularly (at least once a year). See the LRB guide and/or look at help password.
• ps -u yourusername --- lists your processes. Contains lots of information about them, including the process ID, which you need if you have to kill a process. Normally, when you have been kicked out of a dialin session or have otherwise managed to get yourself disconnected abruptly, this list will contain the processes you need to kill. Those may include the shell (tcsh or whatever you're using), and anything you were running, for example emacs or elm. Be careful not to kill your current shell - the one with the number closer to the one of the ps command you're currently running. But if it happens, don't panic. Just try again :) If you're using an X-display you may have to kill some X processes before you can start them again. These will show only when you use ps -efl, because they're root processes.
• kill PID --- kills (ends) the processes with the ID you gave. This works only for your own processes, of course. Get the ID by using ps. If the process doesn't 'die' properly, use the option -9. But attempt without that option first, because it doesn't give the process a chance to finish possibly important business before dying. You may need to kill processes for example if your modem connection was interrupted and you didn't get logged out properly, which sometimes happens.
• quota -v --- show what your disk quota is (i.e. how much space you have to store files), how much you're actually using, and in case you've exceeded your quota (which you'll be given an automatic warning about by the system) how much time you have left to sort them out (by deleting or gzipping some, or moving them to your own computer).
• du filename --- shows the disk usage of the files and directories in filename (without argument the current directory is used). du -s gives only a total.
• last yourusername --- lists your last logins. Can be a useful memory aid for when you were where, how long you've been working for, and keeping track of your phonebill if you're making a non-local phonecall for dialling in.
Connecting to the outside world
• nn --- allows you to read news. It will first let you read the news local to turing, and then the remote news. If you want to read only the local or remote news, you can use nnl or nnr, respectively. To learn more about nn type nn, then \tty{:man}, then \tty{=.*}, then \tty{Z}, then hit the space bar to step through the manual. Or look at the man page. Or check out the hypertext nn FAQ - probably the easiest and most fun way to go.
• rlogin hostname --- lets you connect to a remote host
• telnet hostname --- also lets you connect to a remote host. Use rlogin whenever possible.
• ftp hostname --- lets you download files from a remote host which is set up as an ftp-server. This is a common method for exchanging academic papers and drafts. If you need to make a paper of yours available in this way, you can (temporarily) put a copy in /user/ftp/pub/TMP. For more permanent solutions, ask Emma. The most important commands within ftp are get for getting files from the remote machine, and put for putting them there (mget and mput let you specify more than one file at once). Sounds straightforward, but be sure not to confuse the two, especially when your physical location doesn't correspond to the direction of the ftp connection you're making. ftp just overwrites files with the same filename. If you're transferring anything other than ASCII text, use binary mode.
• lynx --- lets you browse the web from an ordinary terminal. Of course you can see only the text, not the pictures. You can type any URL as an argument to the G command. When you're doing this from any Stanford host you can leave out the .stanford.edu part of the URL when connecting to Stanford URLs. Type H at any time to learn more about lynx, and Q to exit.
Miscellaneous tools
• webster word --- looks up the word in an electronic version of Webster's dictionary and returns the definition(s)
• date --- shows the current date and time.
• cal --- shows a calendar of the current month. Use e.g., 'cal 10 1995' to get that for October 95, or 'cal 1995' to get the whole year.
password
When you received your username and password from the consulting desk, the password was a generated password. You should personalize your own password so that it is easy to remember without being something others could easily guess. It should not be a word that is in a dictionary (as a program can be written to try all the words in a dictionary in seconds). Your password has to be at least 6 characters. It can be letters (UPPER case or lower case) or numbers. CHANGE IT!
DO NOT give your password to others. This is an account and you are responsible for what is done on this account. If you give the password to someone else and they do something wrong, your account information will be pointing to you. DO NOT give your password to others.
If or when you change your password, it might take a few minutes for the new password to be activated. There are several changes that must take place on several computers. Be patient. If you just changed your password and the new password doesn't work yet, the old password is still active and it will work.
type this in this is what it will do
sunburst% password you will be prompted to enter your old password
old password enter your old password here
new password you will be asked to enter a new password
new password type it again for verification
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ls (list schema)
The ls command displays the files and directories in your current working directory. If there are no visible files in your directory, the UNIX prompt will be returned. ls does not display hidden files which begin with a . (period). To display all files you must include the option -a.
type this in this is what it will do
sunburst% ls displays the files and directories in your current directory
sunburst% ls -a displays all files and directories (even the hidden ones)
sunburst% ls -l displays all files and directories w/FULL description
sunburst% dir same as ls -l (alias for DOS people)
sunburst% ls -R displays all files and directories in current directory and below (recursive)
You should not delete or change any hidden files. These files are created for administrative use of your e-mail, news readers, login, etc.
________________________________________
mkdir (make directory)
The mkdir command will create a subdirectory inside of your current working directory. If you are logged into sunburst go ahead and try the command as follows.
type this in this is what will happen
sunburst% mkdir tutor_stuff this will create a subdirectory called tutor_stuff
Now let us look to make sure the directory was actually created.
sunburst% ls should display your files and subdirectories in your current working directory (including the subdirectory you just created.)
________________________________________
cd (change directories)
The cd command will change the current working directory to the location or path you type.
sunburst% cd tutor_stuff change the working directory to tutor_stuff
sunburst% cd .. cd followed by .. will take you to the current parent directory
sunburst% cd cd by itself will take you to your home directory
no matter where you currently are
sunburst% cd tutor_stuff change the working directory to tutor_stuff
If you type in the ls command here (make sure you are inside of tutor_stuff) you should see that the directory (you just created) is empty. Try it and see! Now that you are in the directory called tutor_stuff create another subdirectory called more_stuff. We will use this subdirectory later.
________________________________________
touch (touches a file and updates it)
The touch command will update the last time a file was edited. If you touch a file that doesn't yet exist, it will create a file with zero length. You probably won't use it much, but it will allow us to easily create files that we will use and delete later.
sunburst% cd ~/tutor_stuff makes sure everyone is in the right place
sunburst% touch testfile creates a file named testfile
sunburst% ls check to see if the file is there
Create another file of your own choice. Make sure you remember the name so you can delete it later.
________________________________________
pwd (print working directory)
The pwd command shows you where you are (path wise) on the computer (server - not your desktop). You have probably noticed that every time you change directories you get a description of the path. Sometimes it is necessary to know your current path without changing to a different directory.
sunburst% cd takes you to your home directory
sunburst% pwd prints your working directory
you should see something like /home/coyote/username
sunburst% cd tutor_stuff takes you to tutor_stuff subdirectory
sunburst% pwd you should see /home/coyote/username/tutor_stuff
See if you can get back to the more_stuff subdirectory. Next, have the full pathname printed to the screen using the pwd command. (Can you guess what the full pathname will be?)
________________________________________
Miscellaneous stuff about directories and pathnames
Follow the directions and make sure you understand what is happening.
sunburst% cd takes you to your home directory
sunburst% ls lists files and directories in the current directory
sunburst% ls tutor_stuff lists files and directories inside of tutor_stuff
sunburst% ls what is not a directory and will say "what not found"
sunburst% ls ~ lists files and directories in your home directory
(no matter where you currently are in the system)
The tilde (~) is a reference to your home directory.
________________________________________
cp (copy file)
You can make an exact copy of a file using the copy (cp) command.
sunburst% cd ~/tutor_stuff makes sure everyone is in the right place
sunburst% cp testfile file2 makes a copy of testfile and calls it file2
sunburst% dir make sure the files are really there
See if you can make a copy of file2 (call it file3).
________________________________________
mv (move file)
The mv command moves files and directories around in the file system. You can also use the mv command to rename a file. To make sure these examples work you must be inside of tutor_stuff with the testfile and file2 created.
sunburst% mv testfile file1 renames testfile with the name of file1
sunburst% mv file1 .. moves file1 to its parent directory
sunburst% mv file2 more_stuff moves file2 into subdirectory more_stuff
See if you can move the file2 that is in more_stuff back to tutor_stuff. Also move the file1 that is in home directory back to tutor_stuff. If you do this you should have file1, file2, and file3 inside of tutor_stuff. Use the dir or ls commands to make sure you moved the files to the right spots.
________________________________________
rm (remove file)
The rm command removes or deletes files from the file system. You must be careful. DO NOT delete anything you might need later. You can't get it back.
sunburst% rm file1 removes file1
sunburst% rm file3 .. removes file3
Check to see that file2 still exists and that file1 and file3 are gone. Then remove file2.
________________________________________
rmdir (remove directory)
The rmdir command will remove an empty directory. If you have followed closely up to this point you should not have any files in the subdirectory more_stuff, so let's remove that directory.
sunburst% cd ~/tutor_stuff makes sure everyone is in the right place
sunburst% rmdir more_stuff removes directory called more_stuff
See if you can remove the directory tutor_stuff. You need to make sure that there are no files or directories inside. (Remember you created another file of your choice - with a touch command earlier.)
________________________________________
chmod (changing a file mode)
The chmod command lets the owner of a file change the permissions settings for a file or directory. These permissions are displayed with the dir or ls -l listings. The permissions are in the form of
-rwxrwxrwx
This collection of letters tells us how the permissions for a file (starting with a -) or directory (starting with a d) are set. The first three letters give the permissions for the owner of the file. The middle group (next three letters) give us the permissions for the group to which the owner belongs. The last three letters tell the permissions for everyone else. The permissions can be set for directories as well as files but have slightly different meanings.
files
• r- read permission
• w-write permission
• x-execute permission
directories
• r-permission to list files in a directory
• w-permission to delete files or move files
• x-permission to access to files in the directory
permissions
owner group everyone
- rwx rwx rwx
codes r - Read Permission
4
w- Write Permission 2
x- Execute Permission
If you wanted to set a file with full permissions for yourself or owner (4+2+1)=7, read and write permissions for the group (4+2)=6 and read only for everyone 4=4, the command would be
chmod 764 filename.
Depending on what you are doing with (and from) the files, the permissions need to be set appropriately for owner, group and everyone.
________________________________________
du (disk utility)
The du command prints the number of kilobytes you have in each subdirectory. This can be useful to see which directory has the most files if you have gone over quota. From your home directory type
sunburst% du
________________________________________
quota (displays user quota and usage)
Each user on sunburst is allocated a certain amount of disk space (usually about 5 megabytes). If you exceed this quota some of your files must be removed within a certain time period. To check your quota and see how much you are using type
sunburst% quota -v
________________________________________
clear (clears screen)
The command clear just clears your terminal screen. Go ahead and try this. You should see a clear terminal window with sunburst% at the top.
________________________________________
Ways to display file contents
In order for us to experiment with the next five commands, we need to create an example file. To do this you can either type the list below exactly as it appears or you can highlight (or select) the list below and cut-n-paste it into UNIX at the sunburst% prompt. Either way will work the same. In this example we are sending the input from the keyboard into the file demofile. AFTER the list is either typed into UNIX or pasted from Netscape into UNIX you must stop the input with a return and a control-d.
---------------------------list below
cat > demofile
one
two
three
four
five
six
seven
eight
nine
ten
eleven
twelve
thirteen
fourteen
fifteen
sixteen
seventeen
eighteen
nineteen
twenty
twenty-one
twenty-two
twenty-three
twenty-four
twenty-five
twenty-six
------------------list above
AFTER the list is either typed into UNIX or pasted from Netscape into UNIX you must stop the input with a return and a control-d.
________________________________________
cat (concatenate)
The cat command will display the entire contents of the file on the terminal screen. If it is more than one page it will all scroll by quickly.
sunburst% cat demofile displays entire file contents to terminal screen
________________________________________
more (display one screen at a time)
To display the entire file one screen at a time use the more command instead of cat. After each screen is drawn you must hit the space bar to go on to the next screen.
sunburst% more demofile displays the file example one screen at a time
________________________________________
head (display first 10 lines of a file)
The head command will display the first 10 lines of a file.
sunburst% head demofile should display one - ten in our demofile
________________________________________
tail (displays last 10 lines of a file)
displays last 10 lines of a file
sunburst% tail demofile should display seventeen-twenty-six in our file
________________________________________
wc (word count)
The wc command will tell you how many lines, words and characters.
sunburst% wc demofile would return 26 lines 26 words and about 170 letters
If you pasted the info from Netscape there would be a few more letters because of additional spaces used in formatting HTML (approximately 383 letters).
________________________________________
* (wild card - matches none or more )
The * is a wild card that will replace anything in its place. Below are some examples of its use.
sunburst% dir *.gif displays all files ending with .gif
sunburst% dir test* displays all files beginning with test
________________________________________
? (wild card - matches just one character)
The ? is a wild card that will match one character only. Below is an examples of its use.
sunburst% dir test?.gif displays all files starting with test
then valid character
then ending with .gif
would not find test10.gif
________________________________________
file name conventions
Unix file names should contain only letters, numbers, underscore and period (. often referred to as dot). The file names can contain up to 256 characters. Try to give your file names meaning. Don't use all 256 characters.
Directories are basically a special type of file, so the rules for naming files apply to directories also.
________________________________________
!!
This is called the bang bang command. It will repeat the last command entered into unix from your keyboard. This is like the F3 command from DOS.
Try it!
A variation of this is ! followed by a letter (or letters). This will re-issue the last unix command that started with that letter (or letters). Lets look at the following example:
sunburst% dir would display the current working directory
sunburst% !! would repeat last command
sunburst% mkdir stuff creates directory stuff
sunburst% clear clears the terminal window
sunburst% cd stuff change working directory to stuff
sunburst% !c would try to change directories again
this wouldn't work because you are already there
sunburst% !cl would send the last unix command starting with cl which would be clear
________________________________________
More help directly from UNIX here
________________________________________
man
Read the UNIX on line manual page for a specific command.
sunburst% man cp displays online manual for copy command
Notice the --More--(26%) message at the bottom of the screen (if you type the above command). If you do not want to view the remaining pages you can [interrupt Process] with the Control-C command.
________________________________________
whatis
The whatis command will display a one-line explanation of a command.
sunburst% whatis cp displays a one-line description of the cp command
________________________________________
apropos
If you don't remember the UNIX command but you know you want to copy a file you can use the apropos command to find reference to the copy command within the online manual.
sunburst% apropos copy displays references to copy within the online manuals
________________________________________
A little fun?
________________________________________
finger
If you want to find out some information about another user (such as: are they logged on, when did they read their mail last, do they have a plan) you can use the finger command. The finger command reads some of those invisible files in your directory we were talking about earlier to display the information you will see on your screen.
sunburst% finger username@host displays information regarding the person you are checking on
________________________________________
talk
If you fingered someone and know that they are currently logged into sunburst you can talk to them. The talk command will split your window into a upper portion and lower portion. You will type on one and read the person's responses an the other port ion. It is kind of like a telephone (well no sound). You can do this with anyone in the world that is logged on if you know their e-mail address.
After you issue the talk command the other person should see a message that says you are requesting to talk to them. If they want to talk to you they need to type in a corresponding message on their computer screen.
UNIX Commands
UNIX COMMANDS
The cat command reads one or more files and prints them to standard output. The operator > can be used to combine multiple files into one. The operator >> can be used to append to an existing file.
The syntax for the cat command is:
cat [options] [files]
options:
-e $ is printed at the end of each line. This option must be used with -v.
-s Suppress messages pertaining to files that do not exist.
-t Each tab will display as ^I and each form feed will display as ^L. This option must be used with -v.
-u Output is printed as unbuffered.
-v Display control characters and nonprinting characters
Examples:
cat file1
cat file1 file2 > all
cat file1 >> file2
The cd command changes directory.
The syntax for the cd command is:
cd [dir]
Examples:
cd tech
cd /tech
The chmod command changes the access mode of one file or multiple files.
The syntax for the chmod command is:
chmod [option] mode files
options:
-R Descend directory arguments recursively while setting modes.
-f Suppress error messages if command fails.
mode:
Who u=user, g=group, o=other, a=all (default)
Opcode + means add permission
- means remove permission
= means assign permission and remove the permission of unspecified fields
Permission r=Read, w=write, x=Execute, s=set uid bit, t=sticky bit
u=user, g=group, o=other, l=mandatory locking
Examples:
chmod 751 tech
chmod u=rwx, g=rx, o=x tech
chmod =r tech
The ftp command allows you to transfer files to and from a remote server.
The syntax for the ftp command is:
ftp [options] [hostname]
options:
-d Debugging is enabled.
-g Filename globbing is disabled.
-i Interactive prompting is disabled.
-n When you are initially connecting, auto-login is disabled.
-v Display all responses from the server.
Examples:
ftp tech
ftp -v tech
The grep command allows you to search one file or multiple files for lines that contain a pattern. Exit status is 0 if matches were found, 1 if no matches were found, and 2 if errors occurred.
The syntax for the grep command is:
grep [options] pattern [files]
options:
-b Display the block number at the beginning of each line.
-c Display the number of matched lines.
-h Display the matched lines, but do not display the filenames.
-i Ignore case sensitivity.
-l Display the filenames, but do not display the matched lines.
-n Display the matched lines and their line numbers.
-s Silent mode.
-v Display all lines that do NOT match.
-w Match whole word.
Examples:
grep -c tech file1
The kill command allows you to kill one process ID or multiple process IDs.
The syntax for the kill command is:
kill [options] IDs
options:
-l Lists the signal names.
-signal The signal number of name. Using the signal number of 9, means that the kill is absolute.
Examples:
kill -9 78689
The ls command lists all files in the directory that match the name. If name is left blank, it will list all of the files in the directory.
The syntax for the ls command is:
ls [options] [names]
options:
-a Displays all files.
-b Displays nonprinting characters in octal.
-c Displays files by file timestamp.
-C Displays files in a columnar format (default)
-d Displays only directories.
-f Interprets each name as a directory, not a file.
-F Flags filenames.
-g Displays the long format listing, but exclude the owner name.
-i Displays the inode for each file.
-l Displays the long format listing.
-L Displays the file or directory referenced by a symbolic link.
-m Displays the names as a comma-separated list.
-n Displays the long format listing, with GID and UID numbers.
-o Displays the long format listing, but excludes group name.
-p Displays directories with /
-q Displays all nonprinting characters as ?
-r Displays files in reverse order.
-R Displays subdirectories as well.
-t Displays newest files first. (based on timestamp)
-u Displays files by the file access time.
-x Displays files as rows across the screen.
-1 Displays each entry on a line.
Examples:
ls -la
The mail command allows you to read or send mail. If users is left blank, it allows you to read mail. If users has a value, then it allows you send mail to those users.
The syntax for the mail command is:
mail [options] [users]
options for reading mail:
-e Check if mail exists. Exit status is 0 if mail exists and 1 if mail does not exist.
-f file Read mail from mailbox called file.
-F names Forward mail to names.
-h Displays messages in a window.
-i Ignore interrupts
-p Displays all messages.
-P Displays all messages with header lines.
-q Terminate when an interrupt occurs.
-r Displays oldest messages first.
-U Convert uucp-type addresses to Internet format.
-v Verbose.
options for sending mail:
-m type Display a "Message-type:" line at the heading of the message, followed by type.
-t Display a "To:" line at the heading of the message with the names of the recipients.
-w Send mail to users without waiting for a remote transfer program to finish.
-F Save message in a file called the name of the first recipient.
-h n If message has not been sent after n network connections, do not send message.
-i Ignore interrupts
-r address address is the return address for mail messages.
-s subject Displays subject in the subject header.
-U Convert uucp-type addresses to Internet format.
-v Verbose.
The man command displays the online manual pages.
The syntax for the man command is:
man [options] [ [section] subjects]
options:
- Output is piped through the more command.
-d Debug.
-F Search the MANPATH directories.
-f files Display a summary (one line) for each file.
-k keywords Displays the header lines that contain any of the keywords.
-M path Searchs in the path instead of the MANPATH directories.
-t Format the pages with troff.
-T mac Display using mac.
Examples:
man -f tech
The mkdir command creates a single directories or multiple directories.
The syntax for the mkdir command is:
mkdir [options] directories
options:
-m mode Sets the access mode for the new directory.
-p If the parent directories don't exist, this command creates them.
Examples:
mkdir -m 444 tech
mkdir -p tech/net/faqs
The more command displays the file called name in the screen. The RETURN key displays the next line of the file. The spacebar displays the next screen of the file.
The syntax for the more command is:
more [options] [files]
options:
-c Page through the file by clearing the window. (not scrolling).
-d Displays "Press space to continue, 'q' to quit"
-f Count logical lines rather than screen lines (wrapping text)
-l Ignores form feed (^L) characters.
-r Display all control characters.
-s Displays multiple blank lines as one blank line.
-u Does not display underline characters and backspace (^H).
-w Waits for a user to press a key before exiting.
-n Displays n lines per window.
+num Displays the file starting at line number num.
+/pattern Displays the file starting at two lines before the pattern.
Examples:
more -d tech
The mv command allows you to move and rename files.
The syntax for the mv command is:
mv [options] sources target
options:
-f Forces the move.
-i Prompt for a confirmation before overwriting any files.
Examples:
mv -f tech /usr
The passwd command changes the password for the user.
The syntax for the passwd command is:
passwd [options] [user]
options:
-s Displays password information.
Examples:
passwd tech
The ps command displays active processes.
The syntax for the ps command is:
ps [options]
options:
-a Displays all processes on a terminal, with the exception of group leaders.
-c Displays scheduler data.
-d Displays all processes with the exception of session leaders.
-e Displays all processes.
-f Displays a full listing.
-glist Displays data for the list of group leader IDs.
-j Displays the process group ID and session ID.
-l Displays a long listing
-plist Displays data for the list of process IDs.
-slist Displays data for the list of session leader IDs.
-tlist Displays data for the list of terminals.
-ulist Displays data for the list of usernames.
Examples:
ps -ef
ps -aux
The pwd command displays the full pathname of the current directory.
The syntax for the pwd command is:
pwd
The su command creates a shell with the user ID of another user.
The syntax for the su command is:
su [option] [user] [shell_args]
options:
- Complete the entire login sequence.
Examples:
su root
su tech
The tail command displays the last ten lines of the file.
The syntax for the tail command is:
tail [options] [file]
options:
-f Follow the file as it grows.
-r Displays the lines in the reverse order.
-n[k] Displays the file at the nth item from the end of the file.
+n[k] Displays the file at the nth item from the beginning of the file.
Examples:
tail -r tech
The telnet command allows you to communicate to another host using the TELNET protocol.
The syntax for the telnet command is:
telnet [host [port]]
The vi command launches the text editor called vi.
The syntax for the vi command is:
vi [options] [files]
options:
-ccommand Launch vi and execute the command in vi.
-l Edit a LISP file.
-L Lists all files that were saved due to an editor or system crash.
-rfile Recover and open file after an editor or system crash.
-R Read-only.
+ Position on last line of file in vi.
+n Position on n line of the file in vi.
Examples:
vi + tech
The whoami command displays your username.
The syntax for the whoami command is:
whoami
The whois command searches for the person, login, handle, or organization called name.
The syntax for the whois command is:
whois [option] name
options:
-h host Searches on host name called host.
Examples:
whois tech
The cat command reads one or more files and prints them to standard output. The operator > can be used to combine multiple files into one. The operator >> can be used to append to an existing file.
The syntax for the cat command is:
cat [options] [files]
options:
-e $ is printed at the end of each line. This option must be used with -v.
-s Suppress messages pertaining to files that do not exist.
-t Each tab will display as ^I and each form feed will display as ^L. This option must be used with -v.
-u Output is printed as unbuffered.
-v Display control characters and nonprinting characters
Examples:
cat file1
cat file1 file2 > all
cat file1 >> file2
The cd command changes directory.
The syntax for the cd command is:
cd [dir]
Examples:
cd tech
cd /tech
The chmod command changes the access mode of one file or multiple files.
The syntax for the chmod command is:
chmod [option] mode files
options:
-R Descend directory arguments recursively while setting modes.
-f Suppress error messages if command fails.
mode:
Who u=user, g=group, o=other, a=all (default)
Opcode + means add permission
- means remove permission
= means assign permission and remove the permission of unspecified fields
Permission r=Read, w=write, x=Execute, s=set uid bit, t=sticky bit
u=user, g=group, o=other, l=mandatory locking
Examples:
chmod 751 tech
chmod u=rwx, g=rx, o=x tech
chmod =r tech
The ftp command allows you to transfer files to and from a remote server.
The syntax for the ftp command is:
ftp [options] [hostname]
options:
-d Debugging is enabled.
-g Filename globbing is disabled.
-i Interactive prompting is disabled.
-n When you are initially connecting, auto-login is disabled.
-v Display all responses from the server.
Examples:
ftp tech
ftp -v tech
The grep command allows you to search one file or multiple files for lines that contain a pattern. Exit status is 0 if matches were found, 1 if no matches were found, and 2 if errors occurred.
The syntax for the grep command is:
grep [options] pattern [files]
options:
-b Display the block number at the beginning of each line.
-c Display the number of matched lines.
-h Display the matched lines, but do not display the filenames.
-i Ignore case sensitivity.
-l Display the filenames, but do not display the matched lines.
-n Display the matched lines and their line numbers.
-s Silent mode.
-v Display all lines that do NOT match.
-w Match whole word.
Examples:
grep -c tech file1
The kill command allows you to kill one process ID or multiple process IDs.
The syntax for the kill command is:
kill [options] IDs
options:
-l Lists the signal names.
-signal The signal number of name. Using the signal number of 9, means that the kill is absolute.
Examples:
kill -9 78689
The ls command lists all files in the directory that match the name. If name is left blank, it will list all of the files in the directory.
The syntax for the ls command is:
ls [options] [names]
options:
-a Displays all files.
-b Displays nonprinting characters in octal.
-c Displays files by file timestamp.
-C Displays files in a columnar format (default)
-d Displays only directories.
-f Interprets each name as a directory, not a file.
-F Flags filenames.
-g Displays the long format listing, but exclude the owner name.
-i Displays the inode for each file.
-l Displays the long format listing.
-L Displays the file or directory referenced by a symbolic link.
-m Displays the names as a comma-separated list.
-n Displays the long format listing, with GID and UID numbers.
-o Displays the long format listing, but excludes group name.
-p Displays directories with /
-q Displays all nonprinting characters as ?
-r Displays files in reverse order.
-R Displays subdirectories as well.
-t Displays newest files first. (based on timestamp)
-u Displays files by the file access time.
-x Displays files as rows across the screen.
-1 Displays each entry on a line.
Examples:
ls -la
The mail command allows you to read or send mail. If users is left blank, it allows you to read mail. If users has a value, then it allows you send mail to those users.
The syntax for the mail command is:
mail [options] [users]
options for reading mail:
-e Check if mail exists. Exit status is 0 if mail exists and 1 if mail does not exist.
-f file Read mail from mailbox called file.
-F names Forward mail to names.
-h Displays messages in a window.
-i Ignore interrupts
-p Displays all messages.
-P Displays all messages with header lines.
-q Terminate when an interrupt occurs.
-r Displays oldest messages first.
-U Convert uucp-type addresses to Internet format.
-v Verbose.
options for sending mail:
-m type Display a "Message-type:" line at the heading of the message, followed by type.
-t Display a "To:" line at the heading of the message with the names of the recipients.
-w Send mail to users without waiting for a remote transfer program to finish.
-F Save message in a file called the name of the first recipient.
-h n If message has not been sent after n network connections, do not send message.
-i Ignore interrupts
-r address address is the return address for mail messages.
-s subject Displays subject in the subject header.
-U Convert uucp-type addresses to Internet format.
-v Verbose.
The man command displays the online manual pages.
The syntax for the man command is:
man [options] [ [section] subjects]
options:
- Output is piped through the more command.
-d Debug.
-F Search the MANPATH directories.
-f files Display a summary (one line) for each file.
-k keywords Displays the header lines that contain any of the keywords.
-M path Searchs in the path instead of the MANPATH directories.
-t Format the pages with troff.
-T mac Display using mac.
Examples:
man -f tech
The mkdir command creates a single directories or multiple directories.
The syntax for the mkdir command is:
mkdir [options] directories
options:
-m mode Sets the access mode for the new directory.
-p If the parent directories don't exist, this command creates them.
Examples:
mkdir -m 444 tech
mkdir -p tech/net/faqs
The more command displays the file called name in the screen. The RETURN key displays the next line of the file. The spacebar displays the next screen of the file.
The syntax for the more command is:
more [options] [files]
options:
-c Page through the file by clearing the window. (not scrolling).
-d Displays "Press space to continue, 'q' to quit"
-f Count logical lines rather than screen lines (wrapping text)
-l Ignores form feed (^L) characters.
-r Display all control characters.
-s Displays multiple blank lines as one blank line.
-u Does not display underline characters and backspace (^H).
-w Waits for a user to press a key before exiting.
-n Displays n lines per window.
+num Displays the file starting at line number num.
+/pattern Displays the file starting at two lines before the pattern.
Examples:
more -d tech
The mv command allows you to move and rename files.
The syntax for the mv command is:
mv [options] sources target
options:
-f Forces the move.
-i Prompt for a confirmation before overwriting any files.
Examples:
mv -f tech /usr
The passwd command changes the password for the user.
The syntax for the passwd command is:
passwd [options] [user]
options:
-s Displays password information.
Examples:
passwd tech
The ps command displays active processes.
The syntax for the ps command is:
ps [options]
options:
-a Displays all processes on a terminal, with the exception of group leaders.
-c Displays scheduler data.
-d Displays all processes with the exception of session leaders.
-e Displays all processes.
-f Displays a full listing.
-glist Displays data for the list of group leader IDs.
-j Displays the process group ID and session ID.
-l Displays a long listing
-plist Displays data for the list of process IDs.
-slist Displays data for the list of session leader IDs.
-tlist Displays data for the list of terminals.
-ulist Displays data for the list of usernames.
Examples:
ps -ef
ps -aux
The pwd command displays the full pathname of the current directory.
The syntax for the pwd command is:
pwd
The su command creates a shell with the user ID of another user.
The syntax for the su command is:
su [option] [user] [shell_args]
options:
- Complete the entire login sequence.
Examples:
su root
su tech
The tail command displays the last ten lines of the file.
The syntax for the tail command is:
tail [options] [file]
options:
-f Follow the file as it grows.
-r Displays the lines in the reverse order.
-n[k] Displays the file at the nth item from the end of the file.
+n[k] Displays the file at the nth item from the beginning of the file.
Examples:
tail -r tech
The telnet command allows you to communicate to another host using the TELNET protocol.
The syntax for the telnet command is:
telnet [host [port]]
The vi command launches the text editor called vi.
The syntax for the vi command is:
vi [options] [files]
options:
-ccommand Launch vi and execute the command in vi.
-l Edit a LISP file.
-L Lists all files that were saved due to an editor or system crash.
-rfile Recover and open file after an editor or system crash.
-R Read-only.
+ Position on last line of file in vi.
+n Position on n line of the file in vi.
Examples:
vi + tech
The whoami command displays your username.
The syntax for the whoami command is:
whoami
The whois command searches for the person, login, handle, or organization called name.
The syntax for the whois command is:
whois [option] name
options:
-h host Searches on host name called host.
Examples:
whois tech
Parellel Xtender Examples
Using Transformation Stages Part - 4
Task:
To create a job to extract the source from different stages, sort, join, transform and load in the target file.
Join stage – This stage joins the same two columns of different data. It also varies according to specified condition.
Steps for Job Design:
1. Open Data Stage Designer.
2. Drag the following stages from the palette to the parallel canvas and link the stages as shown below:
a) Dataset Stage (1)
b) DB2 Stage (1)
c) Sort Stage (1)
d) Join Stage (1)
e) Transformer Stage (1)
f) Copy Stage (2)
Job Design:
Parameterization:
1. Click on the Job Properties (Ctrl + J) and then click on the Parameters tab.
2. Type the following:
a) Parameter Name.
b) Prompt.
c) Type.
d) Default Type.
Extraction - 1:
Data Set Stage (UpdatedFinance):
1. Double Click on the Data Set Stage (UpdatedFinance).
2. Click Properties and then click on the property File. Browse for the location (can also be parameterized).
3. Click on the Columns tab and click the load button.
4. Select the Table definition (UpdatedFinance) from the category Dataset and click OK.
5. Click on View Data button.
6. Click OK.
Source - 2:
1. Double click on the DB Stage (Finance).
2. Enter the connection properties (Connection Name, User Id and Password) in the appropriate text boxes (passed through parameter).
3. Click the output tab and browse for the table finance.
4. Click on the Columns tab and then click on the Load button.
5. Select the appropriate Table definition (Finance) from DBMS and click OK.
6. Click on View Data button.
7. Click OK.
Transformation – 1:
Sort Stage (SortFinance):
1. Double click on the Sort Stage (SortFinance)
2. Click Properties tab and key in as shown below:
3. Click on the Output tab -> Mapping tab and map the columns as shown below:
Transformation – 2:
Copy Stage (RenamedFinance)
1. Double click on the Copy Stage and rename the existing column definition as shown below:
2. Click on the Output tab and then click on the Mapping tab.
3. Click OK.
Transformation – 3:
Join Stage (LOJFinance):
1. Double click on the Join Stage (LOJFinance).
2. Click on Properties tab and input as shown below:
3. Click on the Output tab and then map columns as shown below:
4. Click OK.
Transformation – 4:
Transformer Stage (AdjustLoanInfo):
1. Double click on the Transformer Stage.
2. Click on the Stage Properties icon and click on the Variables tab.
3. Key in the following the inputs:
4. Click OK.
5. Map the columns as shown below:
6. The derivations for:
"BALANCE" =
"NEXT_DUE_DATE" =
"STATUS" =
7. Click OK.
Output:
Task:
To create a job to extract the source from different stages, sort, join, transform and load in the target file.
Join stage – This stage joins the same two columns of different data. It also varies according to specified condition.
Steps for Job Design:
1. Open Data Stage Designer.
2. Drag the following stages from the palette to the parallel canvas and link the stages as shown below:
a) Dataset Stage (1)
b) DB2 Stage (1)
c) Sort Stage (1)
d) Join Stage (1)
e) Transformer Stage (1)
f) Copy Stage (2)
Job Design:
Parameterization:
1. Click on the Job Properties (Ctrl + J) and then click on the Parameters tab.
2. Type the following:
a) Parameter Name.
b) Prompt.
c) Type.
d) Default Type.
Extraction - 1:
Data Set Stage (UpdatedFinance):
1. Double Click on the Data Set Stage (UpdatedFinance).
2. Click Properties and then click on the property File. Browse for the location (can also be parameterized).
3. Click on the Columns tab and click the load button.
4. Select the Table definition (UpdatedFinance) from the category Dataset and click OK.
5. Click on View Data button.
6. Click OK.
Source - 2:
1. Double click on the DB Stage (Finance).
2. Enter the connection properties (Connection Name, User Id and Password) in the appropriate text boxes (passed through parameter).
3. Click the output tab and browse for the table finance.
4. Click on the Columns tab and then click on the Load button.
5. Select the appropriate Table definition (Finance) from DBMS and click OK.
6. Click on View Data button.
7. Click OK.
Transformation – 1:
Sort Stage (SortFinance):
1. Double click on the Sort Stage (SortFinance)
2. Click Properties tab and key in as shown below:
3. Click on the Output tab -> Mapping tab and map the columns as shown below:
Transformation – 2:
Copy Stage (RenamedFinance)
1. Double click on the Copy Stage and rename the existing column definition as shown below:
2. Click on the Output tab and then click on the Mapping tab.
3. Click OK.
Transformation – 3:
Join Stage (LOJFinance):
1. Double click on the Join Stage (LOJFinance).
2. Click on Properties tab and input as shown below:
3. Click on the Output tab and then map columns as shown below:
4. Click OK.
Transformation – 4:
Transformer Stage (AdjustLoanInfo):
1. Double click on the Transformer Stage.
2. Click on the Stage Properties icon and click on the Variables tab.
3. Key in the following the inputs:
4. Click OK.
5. Map the columns as shown below:
6. The derivations for:
"BALANCE" =
"NEXT_DUE_DATE" =
"STATUS" =
7. Click OK.
Output:
PX Examples
81.Do you know about INTEGRITY/QUALITY stage?
Ans:Qulaity Stage can be integrated with DataStage, In Quality Stage we have many stages like investigate, match, survivorship like that so that we can do the Quality related works and we can integrate with datastage we need Quality stage plugin to achieve the task.
or
could you please expalin in detail what excatly quality stagestage,auditstage,profilestage used in datastage and where it is used in datastage .
82.How did you handle an 'Aborted' sequencer?
Ans:In almost all cases we have to delete the data inserted by this from DB manually and fix the job and then run the job again.
83.Read the String functions in DS
Ans:Functions like [] -> sub-string function and ':' -> concatenation operator
Syntax: string [ [ start, ] length ]
string [ delimiter, instance, repeats ]
84.What will you in a situation where somebody wants to send you a file and use that file as an input or reference and then run job.
Ans:A. Under Windows: Use the 'WaitForFileActivity' under the Sequencers and then run the job. May be you can schedule the sequencer around the time the file is expected to arrive.
B. Under UNIX: Poll for the file. Once the file has start the job or sequencer depending on the file.
85.What are all the third party tools used in DataStage?
Ans:Autosys, TNG, event coordinator are some of them that I know and worked with
or
Maestro Schedular is another third party tool.........
86.How do you pass filename as the parameter for a job?
Ans:1. Go to DataStage Administrator->Projects->Properties->Environment->UserDefined. Here you can see a grid, where you can enter your parameter name and the corresponding the path of the file.
2. Go to the stage Tab of the job, select the NLS tab, click on the "Use Job Parameter" and select the parameter name which you have given in the above. The selected parameter name appears in the text box beside the "Use Job Parameter" button. Copy the parameter name from the text box and use it in your job. Keep the project default in the text box.
87.How do we do the automation of dsjobs?
Ans:We can call Datastage Batch Job from Command prompt using 'dsjob'. We can also pass all the parameters from command prompt.
Then call this shell script in any of the market available schedulers.
The 2nd option is schedule these jobs using Data Stage director.
88.What about System variables?
Ans:DataStage provides a set of variables containing useful system information that you can access from a transform or routine. System variables are read-only.
@DATE The internal date when the program started. See the Date function.
@DAY The day of the month extracted from the value in @DATE.
@FALSE The compiler replaces the value with 0.
@FM A field mark, Char(254).
@IM An item mark, Char(255).
@INROWNUM Input row counter. For use in constrains and derivations in Transformer stages.
@OUTROWNUM Output row counter (per link). For use in derivations in Transformer stages.
@LOGNAME The user login name.
@MONTH The current extracted from the value in @DATE.
@NULL The null value.
@NULL.STR The internal representation of the null value, Char(128).
@PATH The pathname of the current DataStage project.
@SCHEMA The schema name of the current DataStage project.
@SM A subvalue mark (a delimiter used in UniVerse files), Char(252).
@SYSTEM.RETURN.CODE
Status codes returned by system processes or commands.
@TIME The internal time when the program started. See the Time function.
@TM A text mark (a delimiter used in UniVerse files), Char(251).
@TRUE The compiler replaces the value with 1.
@USERNO The user number.
@VM A value mark (a delimiter used in UniVerse files), Char(253).
@WHO The name of the current DataStage project directory.
@YEAR The current year extracted from @DATE.
REJECTED Can be used in the constraint expression of a Transformer stage of an output link. REJECTED is initially TRUE, but is set to FALSE whenever an output link is successfully written.
Ans:Qulaity Stage can be integrated with DataStage, In Quality Stage we have many stages like investigate, match, survivorship like that so that we can do the Quality related works and we can integrate with datastage we need Quality stage plugin to achieve the task.
or
could you please expalin in detail what excatly quality stagestage,auditstage,profilestage used in datastage and where it is used in datastage .
82.How did you handle an 'Aborted' sequencer?
Ans:In almost all cases we have to delete the data inserted by this from DB manually and fix the job and then run the job again.
83.Read the String functions in DS
Ans:Functions like [] -> sub-string function and ':' -> concatenation operator
Syntax: string [ [ start, ] length ]
string [ delimiter, instance, repeats ]
84.What will you in a situation where somebody wants to send you a file and use that file as an input or reference and then run job.
Ans:A. Under Windows: Use the 'WaitForFileActivity' under the Sequencers and then run the job. May be you can schedule the sequencer around the time the file is expected to arrive.
B. Under UNIX: Poll for the file. Once the file has start the job or sequencer depending on the file.
85.What are all the third party tools used in DataStage?
Ans:Autosys, TNG, event coordinator are some of them that I know and worked with
or
Maestro Schedular is another third party tool.........
86.How do you pass filename as the parameter for a job?
Ans:1. Go to DataStage Administrator->Projects->Properties->Environment->UserDefined. Here you can see a grid, where you can enter your parameter name and the corresponding the path of the file.
2. Go to the stage Tab of the job, select the NLS tab, click on the "Use Job Parameter" and select the parameter name which you have given in the above. The selected parameter name appears in the text box beside the "Use Job Parameter" button. Copy the parameter name from the text box and use it in your job. Keep the project default in the text box.
87.How do we do the automation of dsjobs?
Ans:We can call Datastage Batch Job from Command prompt using 'dsjob'. We can also pass all the parameters from command prompt.
Then call this shell script in any of the market available schedulers.
The 2nd option is schedule these jobs using Data Stage director.
88.What about System variables?
Ans:DataStage provides a set of variables containing useful system information that you can access from a transform or routine. System variables are read-only.
@DATE The internal date when the program started. See the Date function.
@DAY The day of the month extracted from the value in @DATE.
@FALSE The compiler replaces the value with 0.
@FM A field mark, Char(254).
@IM An item mark, Char(255).
@INROWNUM Input row counter. For use in constrains and derivations in Transformer stages.
@OUTROWNUM Output row counter (per link). For use in derivations in Transformer stages.
@LOGNAME The user login name.
@MONTH The current extracted from the value in @DATE.
@NULL The null value.
@NULL.STR The internal representation of the null value, Char(128).
@PATH The pathname of the current DataStage project.
@SCHEMA The schema name of the current DataStage project.
@SM A subvalue mark (a delimiter used in UniVerse files), Char(252).
@SYSTEM.RETURN.CODE
Status codes returned by system processes or commands.
@TIME The internal time when the program started. See the Time function.
@TM A text mark (a delimiter used in UniVerse files), Char(251).
@TRUE The compiler replaces the value with 1.
@USERNO The user number.
@VM A value mark (a delimiter used in UniVerse files), Char(253).
@WHO The name of the current DataStage project directory.
@YEAR The current year extracted from @DATE.
REJECTED Can be used in the constraint expression of a Transformer stage of an output link. REJECTED is initially TRUE, but is set to FALSE whenever an output link is successfully written.
Quality and Integrity Satge
81.Do you know about INTEGRITY/QUALITY stage?
Ans:Qulaity Stage can be integrated with DataStage, In Quality Stage we have many stages like investigate, match, survivorship like that so that we can do the Quality related works and we can integrate with datastage we need Quality stage plugin to achieve the task.
or
could you please expalin in detail what excatly quality stagestage,auditstage,profilestage used in datastage and where it is used in datastage .
82.How did you handle an 'Aborted' sequencer?
Ans:In almost all cases we have to delete the data inserted by this from DB manually and fix the job and then run the job again.
83.Read the String functions in DS
Ans:Functions like [] -> sub-string function and ':' -> concatenation operator
Syntax: string [ [ start, ] length ]
string [ delimiter, instance, repeats ]
84.What will you in a situation where somebody wants to send you a file and use that file as an input or reference and then run job.
Ans:A. Under Windows: Use the 'WaitForFileActivity' under the Sequencers and then run the job. May be you can schedule the sequencer around the time the file is expected to arrive.
B. Under UNIX: Poll for the file. Once the file has start the job or sequencer depending on the file.
85.What are all the third party tools used in DataStage?
Ans:Autosys, TNG, event coordinator are some of them that I know and worked with
or
Maestro Schedular is another third party tool.........
86.How do you pass filename as the parameter for a job?
Ans:1. Go to DataStage Administrator->Projects->Properties->Environment->UserDefined. Here you can see a grid, where you can enter your parameter name and the corresponding the path of the file.
2. Go to the stage Tab of the job, select the NLS tab, click on the "Use Job Parameter" and select the parameter name which you have given in the above. The selected parameter name appears in the text box beside the "Use Job Parameter" button. Copy the parameter name from the text box and use it in your job. Keep the project default in the text box.
87.How do we do the automation of dsjobs?
Ans:We can call Datastage Batch Job from Command prompt using 'dsjob'. We can also pass all the parameters from command prompt.
Then call this shell script in any of the market available schedulers.
The 2nd option is schedule these jobs using Data Stage director.
88.What about System variables?
Ans:DataStage provides a set of variables containing useful system information that you can access from a transform or routine. System variables are read-only.
@DATE The internal date when the program started. See the Date function.
@DAY The day of the month extracted from the value in @DATE.
@FALSE The compiler replaces the value with 0.
@FM A field mark, Char(254).
@IM An item mark, Char(255).
@INROWNUM Input row counter. For use in constrains and derivations in Transformer stages.
@OUTROWNUM Output row counter (per link). For use in derivations in Transformer stages.
@LOGNAME The user login name.
@MONTH The current extracted from the value in @DATE.
@NULL The null value.
@NULL.STR The internal representation of the null value, Char(128).
@PATH The pathname of the current DataStage project.
@SCHEMA The schema name of the current DataStage project.
@SM A subvalue mark (a delimiter used in UniVerse files), Char(252).
@SYSTEM.RETURN.CODE
Status codes returned by system processes or commands.
@TIME The internal time when the program started. See the Time function.
@TM A text mark (a delimiter used in UniVerse files), Char(251).
@TRUE The compiler replaces the value with 1.
@USERNO The user number.
@VM A value mark (a delimiter used in UniVerse files), Char(253).
@WHO The name of the current DataStage project directory.
@YEAR The current year extracted from @DATE.
REJECTED Can be used in the constraint expression of a Transformer stage of an output link. REJECTED is initially TRUE, but is set to FALSE whenever an output link is successfully written.
Ans:Qulaity Stage can be integrated with DataStage, In Quality Stage we have many stages like investigate, match, survivorship like that so that we can do the Quality related works and we can integrate with datastage we need Quality stage plugin to achieve the task.
or
could you please expalin in detail what excatly quality stagestage,auditstage,profilestage used in datastage and where it is used in datastage .
82.How did you handle an 'Aborted' sequencer?
Ans:In almost all cases we have to delete the data inserted by this from DB manually and fix the job and then run the job again.
83.Read the String functions in DS
Ans:Functions like [] -> sub-string function and ':' -> concatenation operator
Syntax: string [ [ start, ] length ]
string [ delimiter, instance, repeats ]
84.What will you in a situation where somebody wants to send you a file and use that file as an input or reference and then run job.
Ans:A. Under Windows: Use the 'WaitForFileActivity' under the Sequencers and then run the job. May be you can schedule the sequencer around the time the file is expected to arrive.
B. Under UNIX: Poll for the file. Once the file has start the job or sequencer depending on the file.
85.What are all the third party tools used in DataStage?
Ans:Autosys, TNG, event coordinator are some of them that I know and worked with
or
Maestro Schedular is another third party tool.........
86.How do you pass filename as the parameter for a job?
Ans:1. Go to DataStage Administrator->Projects->Properties->Environment->UserDefined. Here you can see a grid, where you can enter your parameter name and the corresponding the path of the file.
2. Go to the stage Tab of the job, select the NLS tab, click on the "Use Job Parameter" and select the parameter name which you have given in the above. The selected parameter name appears in the text box beside the "Use Job Parameter" button. Copy the parameter name from the text box and use it in your job. Keep the project default in the text box.
87.How do we do the automation of dsjobs?
Ans:We can call Datastage Batch Job from Command prompt using 'dsjob'. We can also pass all the parameters from command prompt.
Then call this shell script in any of the market available schedulers.
The 2nd option is schedule these jobs using Data Stage director.
88.What about System variables?
Ans:DataStage provides a set of variables containing useful system information that you can access from a transform or routine. System variables are read-only.
@DATE The internal date when the program started. See the Date function.
@DAY The day of the month extracted from the value in @DATE.
@FALSE The compiler replaces the value with 0.
@FM A field mark, Char(254).
@IM An item mark, Char(255).
@INROWNUM Input row counter. For use in constrains and derivations in Transformer stages.
@OUTROWNUM Output row counter (per link). For use in derivations in Transformer stages.
@LOGNAME The user login name.
@MONTH The current extracted from the value in @DATE.
@NULL The null value.
@NULL.STR The internal representation of the null value, Char(128).
@PATH The pathname of the current DataStage project.
@SCHEMA The schema name of the current DataStage project.
@SM A subvalue mark (a delimiter used in UniVerse files), Char(252).
@SYSTEM.RETURN.CODE
Status codes returned by system processes or commands.
@TIME The internal time when the program started. See the Time function.
@TM A text mark (a delimiter used in UniVerse files), Char(251).
@TRUE The compiler replaces the value with 1.
@USERNO The user number.
@VM A value mark (a delimiter used in UniVerse files), Char(253).
@WHO The name of the current DataStage project directory.
@YEAR The current year extracted from @DATE.
REJECTED Can be used in the constraint expression of a Transformer stage of an output link. REJECTED is initially TRUE, but is set to FALSE whenever an output link is successfully written.
Remove duplicates in server job
61.Will the data stage consider the second constraint in the transformer once the first condition is satisfied ( if the link odering is given
Ans:Friends, please try to write correct English first. Use a word processing software. A question becomes quite different when incorrect English is used.
I am rewriting your question in correct English:
"Will Datastage consider the second constraint in the transformer if the first constraint is satisfied (if link ordering is given)?"
62.what are the environment variables in datastage?give some examples?
Ans:Theare are the variables used at the project or job level.We can use them to to configure the job ie.we can associate the configuration file(Wighout this u can not run ur job), increase the sequential or dataset read/ write buffer.
ex: $APT_CONFIG_FILE
Like above we have so many environment variables. Please go to job properties and click on "add environment variable" to see most of the environment variables.
63.What are constraints and derivation?* Explain the process of taking backup in DataStage?*What are the different types of lookups available in DataStage?
Ans:Constraints are used to check for a condition and filter the data. Example: Cust_Id<>0 is set as a constraint and it means and only those records meeting this will be processed further.
Derivation is a method of deriving the fields, for example if you need to get some SUM,AVG etc.
64.what is job control?how it is developed?explain with steps?
Ans:Controlling Datstage jobs through some other Datastage jobs. Ex: Consider two Jobs XXX and YYY. The Job YYY can be executed from Job XXX by using Datastage macros in Routines.
To Execute one job from other job, following steps needs to be followed in Routines.
1. Attach job using DSAttachjob function.
2. Run the other job using DSRunjob function
3. Stop the job using DSStopJob function
65.how to find the number of rows in a sequential file?
Ans:Using Row Count system variable
66.how to implement routines in data stage,have any one has any material for data stage pl send to me?
Ans:there are 3 kind of routines is there in Datastage.
1.server routines which will used in server jobs.
these routines will write in BASIC Language
2.parlell routines which will used in parlell jobs
These routines will write in C/C++ Language
3.mainframe routines which will used in mainframe jobs
68.How can you implement Complex Jobs in datastage
Ans:Complex design means having more joins and more look ups. Then that job design will be called as complex job.We can easily implement any complex design in DataStage by following simple tips in terms of increasing performance also. There is no limitation of using stages in a job. For better performance, Use at the Max of 20 stages in each job. If it is exceeding 20 stages then go for another job.Use not more than 7 look ups for a transformer otherwise go for including one more transformer.Am I Answered for u'r abstract Question.
69.What are Stage Variables, Derivations and Constants?
Ans:stage variable is a variable that executes locally within the stage.constraint is like a filter condition which limits the number of records coming from input according to business rule.derivation is like expression which is used to modify or get some values from input columns.Execution order is stage variable,constraint,derivation.........
or
the right order is..
stage variables
constraints
Derivations
70.What is the flow of loading data into fact & dimensional tables?
Ans:Here is the sequence of loading a datawarehouse.
1. The source data is first loading into the staging area, where data cleansing takes place.
2. The data from staging area is then loaded into dimensions/lookups.
3.Finally the Fact tables are loaded from the corresponding source tables from the staging area.
71.Differentiate Primary Key and Partition Key?
Ans:Primary key is the key we define on the table column or set of columns(composite pk) to make sure all the rows in a table are unique.
Partition key is the key that we use while partition the table(in database), process the source records in ETL(in the etl tools). We should define the partition based on the stages( in datastage) or transformations(in Informationca) we use in the job(Datastage) or mapping(in Informatica).To improve the target load process, we use partition.
If u need more info, plz go through Database doc or Datastage or Informatica doc on
72.What are the difficulties faced in using DataStage ? or what are the constraints in using DataStage ?
Ans:* The issue that i faced with datastage is that, it was very difficult to find the errors from the error code since the error table did not specify the reason for the error. And as a fresher i did not know what the error codes satnd for :)
* Another issue is that the help in the datastage was not of much use since it was not specific and was more general.
* I donot know about other tools since this is the only tool that i have used until now. But it was simple to use so liked using it inspite of above issues.
OR
1. I feel, the most difficult part is understanding the "Datastage director job log error messages'. It doesn't give u in proper readable message.
2.We dont have many date functions available like in Informatica or traditional Relational databases.
3. Datastage is like unique product interms of functions ex: Most of the database or ETL tools use for converting from lower case to upper case : UPPER. The datastage uses "UCASE". Datastage is peculiar when we compare to other ETL tools.
Otherthan that, i dont see any issues with Datastage.
73.How do you execute datastage job from command line prompt?
Ans:u can use dsjob executable command from unix or command line.
Using "dsjob" command as follows.
dsjob -run -jobstatus projectname jobname
74.Types of Parallel Processing?
Ans:Hardware wise there are 3 types of parallel processing systems available:
1. SMP (symetric multiprocessing: multiple CPUs, shared memory, single OS)
2. MPP (Massively Parallel Processing Systems: multiple CPUs each having a personal set of resources - memory, OS, etc, but physically housed on the same machine)
3. Clusters: same as MPP, but physically dispersed (not on the same box & connected via high speed networks).
DS offers 2 types of parallelism to take advantage of the above hardware:
1. Pipeline Parallelism
2. Partition Parallelism
75.What is Modulus and Splitting in Dynamic Hashed File?
Ans:The modulus size can be increased by contacting your Unix Admin.
76.What is the default cache size? How do you change the cache size if needed?
Ans:default size is 128mb and we can change cache size in job properties for particular job and by going to tunables in Administrator for all the jobs across project.
77.Compare and Contrast ODBC and Plug-In stages?
Ans:ODBC : a) Poor Performance.
b) Can be used for Variety of Databases.
c) Can handle Stored Procedures.
Plug-In: a) Good Performance.
b) Database specific.(Only one database)
c) Cannot handle Stored Procedures.
78.How to run a Shell Script within the scope of a Data stage job?
Ans:select the EDIT tab in the toolbar-> choose job properties-> select the job parameters->choose the Before/ After routines ->select the EXCESH command
79.Did you Parameterize the job or hard-coded the values in the jobs?
Ans:hi please send me some real time questions in datastage for interview.
i have interview on sunday for accenture.
how do u implement rank in datastage
80.What are OConv () and Iconv () functions and where are they used?
Ans:iconv is used to convert the date into into internal format i.e only datastage can understand
example :- date comming in mm/dd/yyyy format
datasatge will conver this ur date into some number like :- 740
u can use this 740 in derive in ur own format by using oconv.
suppose u want to change mm/dd/yyyy to dd/mm/yyyy
now u will use iconv and oconv.
ocnv(iconv(datecommingfromi/pstring,SOMEXYZ(seein help which is iconvformat),defineoconvformat))
Ans:Friends, please try to write correct English first. Use a word processing software. A question becomes quite different when incorrect English is used.
I am rewriting your question in correct English:
"Will Datastage consider the second constraint in the transformer if the first constraint is satisfied (if link ordering is given)?"
62.what are the environment variables in datastage?give some examples?
Ans:Theare are the variables used at the project or job level.We can use them to to configure the job ie.we can associate the configuration file(Wighout this u can not run ur job), increase the sequential or dataset read/ write buffer.
ex: $APT_CONFIG_FILE
Like above we have so many environment variables. Please go to job properties and click on "add environment variable" to see most of the environment variables.
63.What are constraints and derivation?* Explain the process of taking backup in DataStage?*What are the different types of lookups available in DataStage?
Ans:Constraints are used to check for a condition and filter the data. Example: Cust_Id<>0 is set as a constraint and it means and only those records meeting this will be processed further.
Derivation is a method of deriving the fields, for example if you need to get some SUM,AVG etc.
64.what is job control?how it is developed?explain with steps?
Ans:Controlling Datstage jobs through some other Datastage jobs. Ex: Consider two Jobs XXX and YYY. The Job YYY can be executed from Job XXX by using Datastage macros in Routines.
To Execute one job from other job, following steps needs to be followed in Routines.
1. Attach job using DSAttachjob function.
2. Run the other job using DSRunjob function
3. Stop the job using DSStopJob function
65.how to find the number of rows in a sequential file?
Ans:Using Row Count system variable
66.how to implement routines in data stage,have any one has any material for data stage pl send to me?
Ans:there are 3 kind of routines is there in Datastage.
1.server routines which will used in server jobs.
these routines will write in BASIC Language
2.parlell routines which will used in parlell jobs
These routines will write in C/C++ Language
3.mainframe routines which will used in mainframe jobs
68.How can you implement Complex Jobs in datastage
Ans:Complex design means having more joins and more look ups. Then that job design will be called as complex job.We can easily implement any complex design in DataStage by following simple tips in terms of increasing performance also. There is no limitation of using stages in a job. For better performance, Use at the Max of 20 stages in each job. If it is exceeding 20 stages then go for another job.Use not more than 7 look ups for a transformer otherwise go for including one more transformer.Am I Answered for u'r abstract Question.
69.What are Stage Variables, Derivations and Constants?
Ans:stage variable is a variable that executes locally within the stage.constraint is like a filter condition which limits the number of records coming from input according to business rule.derivation is like expression which is used to modify or get some values from input columns.Execution order is stage variable,constraint,derivation.........
or
the right order is..
stage variables
constraints
Derivations
70.What is the flow of loading data into fact & dimensional tables?
Ans:Here is the sequence of loading a datawarehouse.
1. The source data is first loading into the staging area, where data cleansing takes place.
2. The data from staging area is then loaded into dimensions/lookups.
3.Finally the Fact tables are loaded from the corresponding source tables from the staging area.
71.Differentiate Primary Key and Partition Key?
Ans:Primary key is the key we define on the table column or set of columns(composite pk) to make sure all the rows in a table are unique.
Partition key is the key that we use while partition the table(in database), process the source records in ETL(in the etl tools). We should define the partition based on the stages( in datastage) or transformations(in Informationca) we use in the job(Datastage) or mapping(in Informatica).To improve the target load process, we use partition.
If u need more info, plz go through Database doc or Datastage or Informatica doc on
72.What are the difficulties faced in using DataStage ? or what are the constraints in using DataStage ?
Ans:* The issue that i faced with datastage is that, it was very difficult to find the errors from the error code since the error table did not specify the reason for the error. And as a fresher i did not know what the error codes satnd for :)
* Another issue is that the help in the datastage was not of much use since it was not specific and was more general.
* I donot know about other tools since this is the only tool that i have used until now. But it was simple to use so liked using it inspite of above issues.
OR
1. I feel, the most difficult part is understanding the "Datastage director job log error messages'. It doesn't give u in proper readable message.
2.We dont have many date functions available like in Informatica or traditional Relational databases.
3. Datastage is like unique product interms of functions ex: Most of the database or ETL tools use for converting from lower case to upper case : UPPER. The datastage uses "UCASE". Datastage is peculiar when we compare to other ETL tools.
Otherthan that, i dont see any issues with Datastage.
73.How do you execute datastage job from command line prompt?
Ans:u can use dsjob executable command from unix or command line.
Using "dsjob" command as follows.
dsjob -run -jobstatus projectname jobname
74.Types of Parallel Processing?
Ans:Hardware wise there are 3 types of parallel processing systems available:
1. SMP (symetric multiprocessing: multiple CPUs, shared memory, single OS)
2. MPP (Massively Parallel Processing Systems: multiple CPUs each having a personal set of resources - memory, OS, etc, but physically housed on the same machine)
3. Clusters: same as MPP, but physically dispersed (not on the same box & connected via high speed networks).
DS offers 2 types of parallelism to take advantage of the above hardware:
1. Pipeline Parallelism
2. Partition Parallelism
75.What is Modulus and Splitting in Dynamic Hashed File?
Ans:The modulus size can be increased by contacting your Unix Admin.
76.What is the default cache size? How do you change the cache size if needed?
Ans:default size is 128mb and we can change cache size in job properties for particular job and by going to tunables in Administrator for all the jobs across project.
77.Compare and Contrast ODBC and Plug-In stages?
Ans:ODBC : a) Poor Performance.
b) Can be used for Variety of Databases.
c) Can handle Stored Procedures.
Plug-In: a) Good Performance.
b) Database specific.(Only one database)
c) Cannot handle Stored Procedures.
78.How to run a Shell Script within the scope of a Data stage job?
Ans:select the EDIT tab in the toolbar-> choose job properties-> select the job parameters->choose the Before/ After routines ->select the EXCESH command
79.Did you Parameterize the job or hard-coded the values in the jobs?
Ans:hi please send me some real time questions in datastage for interview.
i have interview on sunday for accenture.
how do u implement rank in datastage
80.What are OConv () and Iconv () functions and where are they used?
Ans:iconv is used to convert the date into into internal format i.e only datastage can understand
example :- date comming in mm/dd/yyyy format
datasatge will conver this ur date into some number like :- 740
u can use this 740 in derive in ur own format by using oconv.
suppose u want to change mm/dd/yyyy to dd/mm/yyyy
now u will use iconv and oconv.
ocnv(iconv(datecommingfromi/pstring,SOMEXYZ(seein help which is iconvformat),defineoconvformat))
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