KSH For Loop Examples

KSH Scripting – for loop syntax

The syntax is as follows:

for {Variable} in {lists}
do
	echo ${Variable}
done

Here is sample shell script to print welcome message 5 times:

#!/bin/ksh
for i in 1 2 3 4 5
do
  echo "Welcome $i times"
done

Run script as follows:
$ chmod +x script.ksh
$ ./script.ksh
OR
$ ksh script.ksh
Where,

• i is variable name
• 1 2 3 4 5 is argument list. It can be any list of words, strings, or numbers. We can also use a shell command or shell metacharacter.
• echo "Welcome $i times" is statement/command to execute five times as per argument list. In this case run echo command 5 times.

ksh for loop examples

You can easily set ranges (1 to 10) as follows:

#!/bin/ksh
for i in {1..10}
do
  echo "Welcome $i times"
done

If above failed to work try the seq command as command substitution in a Korn shell:

#!/usr/bin/ksh
for var in $(seq 1 10)
do
     echo "$var"
done

You can also use variables to define the item list. They will be checked ONLY ONCE, when you start the loop.

#!/bin/ksh
files="/etc/passwd /etc/group /etc/hosts"
for f in $files; do
	if [ ! -f $f ]
	then
 		echo "$f file missing!"
	fi
done

Please do NOT quote “$list”, if you want the for command to use multiple items. Another example using for explicit list:

#!/bin/ksh
for car in bmw ford toyota nissan
   do
   print "Value of car is: $car"
done

KSH for loop command substitution

Create a text file called spaceshuttles.txt as follows:

columbia
endeavour
challenger
discovery
atlantis
enterprise
pathfinder

Now create a shell script called demo.ksh

#!/bin/ksh
for shuttle in $(cat  spaceshuttles.txt)
do
        print "Current Space Shuttle : $shuttle"
done

You can also print file names in /tmp directory:

#!/bin/ksh
for f in $(ls /tmp/*)
do
        print "Full file path  in /tmp dir : $f"
done

Using command line arguments with ksh loops

In this example, the data entered on the command line becomes the argument list of the for loop:

#!/bin/ksh
for arg in $*
do
	echo "Command line arg: $arg"
done

Run it as follows:
$ ./script This is a test

Conclusion

In this quick tutorial, you learned how to write a script with a for loop construct when using ksh. See ksh man page for more information by typing the following man command:
$ man ksh
This repo contains the ksh93u+ and ksh93v- versions of KSH.