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1. Computer Science Lab 1

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SShheellll SSccrriippttiinngg ((CC sshheellll))
by

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

4. 4
CC SShheellll
#! /bin/csh
 set name = hello -> echo $name
$array = ( element1 elemsnt2 )
$array[1] , $array[2]

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CC SShheellll –– FFiirrsstt SSccrriipptt
 ${LOGNAME}
– Print user’s name
 `unix command`
– Enclosed in back quotes
– Performed command substitution
– Ex) `date`
 uname –n
– Display the machine name
 ps –ef | grep “^ *$LOGNAME”
– User’s processes are printed
 chmond –u+x greetme

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CC sshheellll GGeettttiinngg UUsseerr IInnppuutt
$<
– user input (std) without newline
$array = ($name)
– An array is created
Arithmetic ( operators ): @ integer
+ , - , / , * , % , << , >>
+= , -=, *=, /=, ++, --
• Ex) @ sum = 4+6
– Space is required after @

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CCsshheellll DDeebbuuggggiinngg ssccrriippttss
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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c Cshell coommmmaanndd lliinnee aarrgguummeenntt
$0 - The name of the script
$1, $2, $3,..${10}
– Parameters are referenced by number
$* - All positional parameters
$argv[1], $argv[2]
– The first argument , second …
$argv[*] or $argv – all arguments
$#argv – The number of arguments (size)
$argv[$#argv] – The last argument

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Cshell Conditional ccoonnssttrruuccttss
 == , != , <, > , >= , <= , !
 =~ , !~
– String matches ex) $ans =~ [Yy]*
|| , &&
– Logical operator

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CCsshheellll iiff eexxaammpplleess
IIff(( eexxpprreessssiioonn )) tthheenn
CCoommmmaanndd
eellssee
CCoommmmaanndd
eennddiiff
Ex) if ( $#argv != 1) then
echo “$0 requires an argument”
exit 1
endif

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CCsshheellll iiff eexxpprreessssiioonn
 set name = $<
If( “$name” != “” ) then
grep “$name” data file
endif
 If( $answer =~ [Yy]* ) then
mail bob < message
else
mail jon < datafile
endif
 set x = 1 , y = 2, z = 3
If( (“$x” && “$y”) || ! “$z”) then
echo TRUE
 If( $#argv == 0 ) exit 1

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CCsshheellll iiff ccoommmmaanndd
 If { (command) } then
command
endif
 If { ( who | grep $1 >& /dev/null ) } then
echo $1 is logged on
endif
 startover:
set grade = $<
if( “$grade” < 0 || “$grade” > 100 ) then
echo “Illegal grade”
goto startover
endif

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CCsshheellll iiff ffiillee tteessttiinngg
 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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CCsshheellll SSwwiittcchh
set color = $<
sswwiittcchh ((“$color”))
ccaassee bl*::
echo I feel $color
bbrreeaakkssww
ddeeffaauulltt::
echo $color not one of them
bbrreeaakkssww
eennddssww

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CCsshheellll ffoorr
ffoorreeaacchh vvaarriiaabbllee ((wwoorrddlliisstt))
ccoommmmaannddss
eenndd
– foreach person ( bob sam sue fred)
mail $person < letter
end
– foreach person (`cat maillist`)
mail $person <<EOF
Hi $person
EOF
end

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CCsshheellll wwhhiillee
 set num = 0
wwhhiillee ($num < 10 )
echo $num
@ num++
eenndd
 rreeppeeaattee takes two argument( number, command)
– Ex) %repeate 3 echo hello
hello
hello
hello

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CCsshheellll WWhhiillee
sshhiifftt 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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CCsshheellll WWhhiillee
break && continue command
set answer = $<
while( “$answer” !~ [Mm]* )
echo “Wrong! Try again.”
set answer = $<
if( “$answer” =~ [Mm]*) break;
end

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PPrrooggrraammmmiinngg wwiitthh CC sshheellll
mailingList
– data
• Hello XXX,
– friends ( emails )

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RReessoouurrcceess
Our sites
 http://vibranttechnologies.co.in/
 http://vibrantgroupmumbai.blogspot.in/

21. Computer Science Lab 21