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Scripting in Windows and Linux

Scripting in Windows and Linux. What is scripting? What is it for? DOS/Windows batch files Windows Environment Variables Example batch files UNIX/Linux shell scripting Linux Environment Variables Example shell scripts Conclusion. What is scripting? What is it for?.

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Scripting in Windows and Linux

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  1. Scripting in Windows and Linux • What is scripting? • What is it for? • DOS/Windows batch files • Windows Environment Variables • Example batch files • UNIX/Linux shell scripting • Linux Environment Variables • Example shell scripts • Conclusion

  2. What is scripting? What is it for? • Scripting is an extension of the text-based command-line interface • Instead of repetitively typing in a sequence of commands, put them in a file, then just “run” the file with a single command • The basic concept is a bit like macros in a spreadsheet or word processor • Automation of repetitive commands reduces errors • A flexible scripting system becomes a “system programming language” • A good scripting system allows complex tasks to be automated

  3. DOS and Windows • Early PC’s had DOS (Disc Operating System), a text-only command-line interface • Current systems use GUIs • Automation is simpler in text-based systems – so batch scripts are still useful • Windows NT (3.5, 2000, XP and so on) have an enhanced command-line interface • The examples that follow give a glimpse into the style of command shell batch scripting • Many batch files to file or directory manipulation. • Often they need contextual information contained in the system’s “environment variables”

  4. Some NT Environment Variables ALLUSERSPROFILE=C:\Documents and Settings\All Users APPDATA=C:\Documents and Settings\nas1\Application Data CLASSPATH="C:\WINDOWS\system32\QTJava.zip" CommonProgramFiles=C:\Program Files\Common Files … NUMBER_OF_PROCESSORS=2 OS=Windows_NT PATHEXT=.COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH PROCESSOR_ARCHITECTURE=x86 PROCESSOR_IDENTIFIER=x86 Family 15 Model 2 Stepping 9, GenuineIntel PROCESSOR_LEVEL=15 PROCESSOR_REVISION=0209 … USERPROFILE=C:\Documents and Settings\nas1 windir=C:\WINDOWS WINVERSION=XP

  5. Examples: NT command-line @echo off rem Checks which machine we're running on first... if "%USERNAME%"=="nas1" goto MachineOK echo No! Wrong Machine!!!! goto EndOfScript :MachineOK echo Yes! This is the right machine. :EndOfScript

  6. @echo off echo @echo off > allMyXLS.bat echo rem Built by robots! >> allMyXLS.bat for %%x IN (*.xls) DO echo print %%x >> allMyXLS.bat echo rem All done >> allMyXLS.bat call allMyXLS.bat @echo off rem Built by robots! print attendanceS2_Feb2006.xls print CPU_Speed_Intel.xls print CPU_Speed_Intel_v2.xls print csa marks 2005-6.xls rem All done More complex batch files

  7. @echo off set theDate=%date% set theDate2=%theDate:/=-% md %theDate2% copy *.xls %theDate2% set theDate= set theDate2= This example creates two environment variables, uses one then destroys both The first variable holds the date (e.g. 28/07/2009), the second holds a modified form of the first (e.g. 28-07-2009) The second date is used to create a subdirectory Files are copied into the subdirectory This is a simple “daily backup” script Useful but convoluted?

  8. UNIX/Linux shell scripting • There are a few different command-line systems or “shells” for Linux • The Bourne shell (sh), the original UNIX shell. • The C-shell (csh), better for interactive users • The tc-shell (tcsh), an improved C-shell • The Korn shell (ksh), a commercial (and improved) Bourne shell • The “Bourne again” shell (bash), a free, improved Bourne shell with csh-like elements - very popular, part of Linux • The Z shell (zsh), Bourne-like with many extra features See: http://www.faqs.org/faqs/unix-faq/shell/shell-differences/

  9. Some Linux Environment Variables • USERNAME • HOSTNAME • LOGNAME • MAIL • EDITOR - Specifies the editor to be used by default for some commands such as edquota. Usually it is set to vi or emacs with a command like "export EDITOR=emacs". • TERM - The type of terminal being used. • PATH - The path the system looks in to find commands that the user has entered. • HOME - The current user's home directory • SHELL - The current shell program that is being executed • USER - The name of the current user. • TMPDIR - Allows programs that use the tempnam(3) function call to use the directory specified by this variable rather than the /tmp directory. • SHLVL - Shows how many shells the user has invoked.

  10. Example shell scripts #!/bin/Bash echo Type in a message read sTextInput echo `$sTextInput ` is: $sTextInput #exit 0 Type in a message This is a simple bash demonstration $sTextInput is: This is a simple bash demonstration

  11. Example shell scripts #!/bin/Bash # be sure the directory /mnt exists if [ ! -d /mnt ] then mkdir /mnt fi for i in /mnt/floppy/*; do if [ -f $i ]; then # if the file is there filename=${i#/mnt/floppy/} echo copying $i to /etc/$filename cp -p $i /etc/$filename Fi done

  12. XKCD - Command Line Fu http://xkcd.com/196/

  13. Conclusion • Scripting is very useful • NT provides many useful tools for automation • However, Linux Bash scripting is far more like programming than NT batch scripting • In general, Bash is more powerful than the NT shell • UNIX is fifteen years more mature than Windows, so you might expect a difference • UNIX was a text-only minicomputer OS for a long time, so text-based systems are very well developed • Bash scripting, online book: http://www.linux.com/guides/abs-guide/

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