Shell Scripting (C shell)

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Shell Scripting (C shell)

• SungHo Maeung (sxm3011_at_cs.rit.edu)
• 10/27/2000Tutorial section
• Computer Science Lab

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Contents

• C shell
• First Script
• Getting User Input
• Command Line Arguments
• Conditionals and File Testing
• Switch Loops
• Programming with C Shell
• mailingList
• Summary Resources

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C Shell

• ! /bin/csh
• set name hello -gt echo name
• array ( element1 elemsnt2 )
• array1 , array2

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C Shell First Script

• LOGNAME
• Print users name
• unix command
• Enclosed in back quotes
• Performed command substitution
• Ex) date
• uname n
• Display the machine name
• ps ef grep LOGNAME
• Users processes are printed
• chmond ux greetme

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C shell Getting User Input

• lt
• user input (std) without newline
• array (name)
• An array is created
• Arithmetic ( operators ) _at_ integer
• , - , / , , , ltlt , gtgt
• , -, , /, , --
• Ex) _at_ sum 46
• Space is required after _at_

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Cshell Debugging scripts

• Echo (-x) and Verbose (-v)
• csh x scriptname (command )
• Display each line after variable substitution and
  before execution
• set echo , unset ( in the file )

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Cshell command line argument

• 0 - The name of the script
• 1, 2, 3,..10
• Parameters are referenced by number
• - All positional parameters
• argv1, argv2
• The first argument , second
• argv or argv all arguments
• argv The number of arguments (size)
• argvargv The last argument

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Cshell Conditional constructs

• , ! , lt, gt , gt , lt , !
• , !
• String matches ex) ans Yy
• ,
• Logical operator

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Cshell if examples

• If( expression ) then
• Command
• else
• Command
• endif
• Ex) if ( argv ! 1) then
• echo 0 requires an argument
• exit 1
• endif

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Cshell if expression

• set name ltIf( name ! ) then
• grep name data file
• endif
• If( answer Yy ) then
• mail bob lt message
• else
• mail jon lt datafile
• endif

• set x 1 , y 2, z 3If( (x y) !
  z) then echo TRUE
• If( argv 0 ) exit 1

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Cshell if command

• If (command) then command endif
• If ( who grep 1 gt /dev/null ) then echo
  1 is logged onendif
• startoverset grade ltif( grade lt 0
  grade gt 100 ) then echo Illegal grade goto
  startover
• endif

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Cshell if file testing

• if( ! e file ) file exists
• if( -d file ) a direcotry file
• if( -f file ) a plain file
• if( ! z file ) zero length
• if( -r file -w file) readable and writable
• if( -x file ) executable

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Cshell Switch

• set color ltswitch (color)case bl echo
  I feel color breakswdefault echo color not
  one of them breakswendsw

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Cshell for

• foreach variable (wordlist) commandsend
• foreach person ( bob sam sue fred) mail person
  lt letterend
• foreach person (cat maillist) mail person
  ltltEOF Hi person EOFend

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Cshell while

• set num 0while (num lt 10 ) echo num _at_
  numend
• repeate takes two argument( number, command)
• Ex) repeate 3 echo hellohellohellohello

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Cshell While

• shift command
• Shifts the argv array by one word
• Ex) While( argv) echo argv shift
  end loop a b c a b c b c c

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Cshell While

• break continue command set answer lt
  while( answer ! Mm ) echo Wrong\! Try
  again. set answer lt if( answer Mm)
  break end

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Programming with C shell

• mailingList
• data
• Hello XXX,
• friends ( emails )

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Resources

• Tutorial sites
• http//tobias.fritz.net/cs/csh-programming.htmlA
• http//www.msi.umn.edu/dudley/cshell/programming.
  html
• http//dpleated.ee.ic.ac.uk/unix/old/shell/cshell/
  prog/intro.html