Special shell variables
There are some variables which are set internally by the shell and which are available to the user:

Name Description
——————————————————————————–
$1 – $9 these variables are the positional parameters.

$0 the name of the command currently being executed.

$# the number of positional arguments given to this
invocation of the shell.

$? the exit status of the last command executed is
given as a decimal string. When a command
completes successfully, it returns the exit status
of 0 (zero), otherwise it returns a non-zero exit
status.

$$ the process number of this shell – useful for
including in filenames, to make them unique.

$! the process id of the last command run in
the background.

$- the current options supplied to this invocation
of the shell.

$* a string containing all the arguments to the
shell, starting at $1.

$@ same as above, except when quoted.

Branching
if then fi
if [[ $value -eq 7 ]];then
print "$value is 7"
fi
or:

if [[ $value -eq 7 ]]
then
print "$value is 7"
fior:

if [[ $value -eq 7 ]];then print "$value is 7";fi

if then else fi
if [[ $name = "John" ]];then
print "Your welcome, ${name}."
else
print "Good bye, ${name}!"
fi

if then elif then else fi
if [[ $name = "John" ]];then
print "Your welcome, ${name}."
elif [[ $name = "Hanna" ]];then
print "Hello, ${name}, who are you?"
else
print "Good bye, ${name}!"
fi

case esac
case $var in
john|fred) print $invitation;;
martin) print $declination;;
*) print "Wrong name...";;
esac

——————————————————————————–

Looping Command Syntax for Scripts

while do done
while [[ $count -gt 0 ]];do
print "\$count is $count"
(( count -= 1 ))
done
until do done
until [[ $answer = "yes" ]];do
print -n "Please enter \"yes\": "
read answer
print ""
done
for var in list do done
for foo in $(ls);do
if [[ -d $foo ]];then
print "$foo is a directory"
else
print "$foo is not a directory"
fi
done
continue…break
One can skip the rest of a loop and directly go to the next iteration with: “continue”.

while read line
do
if [[ $line = *.gz ]];then
continue
else
print $line
fi
done
One can also prematurely leave a loop with: “break”.

while read line;do
if [[ $line = *!(.c) ]];then
break
else
print $line
fi
done

http://www.well.ox.ac.uk/~johnb/comp/unix/ksh.html

Removing accounts from predefine list:

#!/bin/ksh

done

Or course, the sleep there is just for aesthetic.. I want to see the screen

    for arg in list
do
...Handle $arg...
done

Real life application..

# ls -l | awk ‘{print$9}’

user01
user02
user03
user04
user05
user06
user07
user08
user09
# pwd
/home
# for x in `ls -l | awk ‘{print$9}’`
> do
> chown $x $x
> done
# ls -aslt
total 136

.. yeah you know what the output is..