Shell Scripting What is Shell Programming? Putting UNIX commands in a file Seldom used where speed is important Often used to manipulate files To create a simple shell script file: $ vi test.sh or $ cat > test.sh To execute a shell script file: $ sh filename Or $./filename

Basic Operators Arithematic Operators : [+, -, \*, /, %, =,!=,==.] Relational Operators : [-eq,-ne,-gt,-lt,-ge,-le] Boolean Operators : [-o,-a,!] String Operators : [ -z, -n, =, !=, str ] File Test operators : [ -b,-c,-d,-e,-f,-r,-w,-x, -s]

Shell Decision Statement If..else statements if [ condition(s) ] then command(s) fi case...esac Statement case word in pattern1) Statement(s) to be executed if pattern1 matches ;; esac

Iterative/Looping Statements While Loop while [ condition ] do Command (s) done Until Loop until [ condition ] do command (s) done For Loop for var in word1 word2... wordN do Command(s) done

String Handling and Command line arguments String handling with test command  test str  test –n str  test –z str String handling with expr command  Length of the string : n=`expr "$str" : ‘.*’` ;  Extracting a sub-string: ` expr “$str” : ‘……\(..\)’` Command line arguments The command-line arguments $1, $2, $3...$9 are also called positional parameters $0 points to actual command/shell script/program Eg: echo “Program name is $0” echo “First argument is $1” echo “Second argument is $2” While executing $ sh test.sh arg1 arg2 Output: Program name is test First argument is arg1 Second argument is arg2