While Loop Syntax help needed

Shell Programming and Scripting
1

Hi everyone,

Can ny1 help me out regarding while loop arguments

i.e. what does

-gt
-ge
-lt
-le

means?

actually i am new to while loops

2

You can find the answers here:

Unix shell scripting with sh/ksh

Regards

3

Simple syntax:

while command_exit_code_is_zero
do
    somecmd1
    somecmd2
done

-lt, -gt, ... are options of test command, look shell builtin test (= also [ ] )

After while is some command line, shell will do it, check exit code and if it's 0 = okay, then do the command lines between do and done.

while true
while cp x y
while (( i < 100 ))
while [ "$some" -lt 100 ]
while test "$some -lt 100
while [ "$some" = "1" ]
while read line
while :
...
: is command, which is builtin and give always exit 0 status ( shell's nop command), do nothing. Today also true and false are builtin commands, so those are more "readable" as :

You can break the loop using command break.

You can jump to the while line using command continue.
ex.

while read line
do
      case "$line" in
           "") continue  ;;    # next line
           end*) break ;;     # end this while
      esac
      do_some_for "$line"
done