Scripting in Windows and Linux

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 PCs 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 systems environment variables

4
Some NT Environment Variables

• ALLUSERSPROFILEC\Documents and Settings\All
  Users
• APPDATAC\Documents and Settings\nas1\Application
  Data
• CLASSPATH"C\WINDOWS\system32\QTJava.zip"
• CommonProgramFilesC\Program Files\Common Files
• NUMBER_OF_PROCESSORS2
• OSWindows_NT
• PATHEXT.COM.EXE.BAT.CMD.VBS.VBE.JS.JSE.WS
  F.WSH
• PROCESSOR_ARCHITECTUREx86
• PROCESSOR_IDENTIFIERx86 Family 15 Model 2
  Stepping 9, GenuineIntel
• PROCESSOR_LEVEL15
• PROCESSOR_REVISION0209
• USERPROFILEC\Documents and Settings\nas1
• windirC\WINDOWS
• WINVERSIONXP

5
Examples NT command-line

• _at_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
More complex batch files

• _at_echo off
• echo _at_echo off gt allMyXLS.bat
• echo rem Built by robots! gtgt allMyXLS.bat
• for x IN (.xls) DO echo print x gtgt
  allMyXLS.bat
• echo rem All done gtgt allMyXLS.bat
• call allMyXLS.bat

• _at_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

7
Useful but convoluted?

• _at_echo off
• set theDatedate
• set theDate2theDate/-
• 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

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 EDITORemacs".
• 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
• filenamei/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/