Working with the Unix OS

Unix Shells
! CASE Statement
case test-string in
pattern-1)
commands
; ;
pattern-2)
commands
; ;
:
esac
TRAP Command
trap commands signal-numbers
Signal Number Conditions
hang up 1 disconnect phone line
terminal interrupt 2 pressing interrupt key
quit 3 pressing ^ \
kill 9 kill command (not -9)
ware terminate 15 default of kill command
Example:
trap '' 15 # prevent script exiting
trap 'echo INTERRUPT; exit l' 2
# remove temporary file on exit command
trap 'rm /tmp/$$.$script 2> /dev/null ' 0
Functions
Functions are either in ".profile" or in scripts that require them.
function-name()
{
commands
}
Example:
wd()
{
cd $1
PS1=" ['pwd'] "
}
Shell Programs
A shell program is simply an ordinary text file containing shell commands. Shell programs are interpreted and
therefore need no compiler. With one minor exception, there is no difference between what can be typed on the
keyboard and what can be written into a shell program.
The exception is that shell programs should start with a comment line: #!/bin/sh
To ensure that if they are executed under a different shell program such as Korn or C Shell, they will be interpreted
by the Bourne Shell.
Shell program files must be made executable: chmod u+x myshellprog
and can be treated like any other unix command.
To trace a shell program, run it using -x option of sh(l}. sh -x ./myshellprog
For more info on shell programming type:
"man sh".
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