CentOS / RHEL: Install KornShell (KSH)

I am porting ksh script from Sun/Oracle Unix to Linux. How do I install ksh (KornShell) in CentOS / Fedora / Red Hat Enterprise Linux? How do I run and test ksh script on RHEL/CentOS Linux?

KSH was developed by David Korn at Bell Labs in 1980s. KSH is is quite popular is quite loved by sysadmins to automate everyday tasks on Unix like operating systems. You can install ksh on CentOS / RHEL. KSH-93 is the most recent version of the KornShell. It is a shell programming language, which is upward compatible with “sh” (the Bourne Shell).

Steps to install ksh in Linux

Open the Terminal app.
Type the ‘yum install ksh‘ command on CentOS/RHEL.
Type the ‘dnf install ksh‘ command on Fedora Linux.
Update your shell in /etc/passwd
Start using your ksh shell.

Let us see steps in detailed to install KornShell (KSH) on a RHEL/CentOS Linux based system.

How to install the Korn Shell (KSH)

Open a terminal and then type the following yum command to install the ksh shell:
$ sudo yum install ksh
OR
# yum install ksh
Sample outputs:

Loaded plugins: auto-update-debuginfo, protectbase, rhnplugin, security
This system is receiving updates from RHN Classic or RHN Satellite.
0 packages excluded due to repository protections
Setting up Install Process
Resolving Dependencies
--> Running transaction check
---> Package ksh.x86_64 0:20100621-19.el6_4.4 will be installed
--> Finished Dependency Resolution
 
Dependencies Resolved
 
================================================================================
 Package  Arch        Version                   Repository                 Size
================================================================================
Installing:
 ksh      x86_64      20100621-19.el6_4.4       rhel-x86_64-server-6      687 k
 
Transaction Summary
================================================================================
Install       1 Package(s)
 
Total download size: 687 k
Installed size: 0  
Is this ok [y/N]: y
Downloading Packages:
ksh-20100621-19.el6_4.4.x86_64.rpm                       | 687 kB     00:00     
Running rpm_check_debug
Running Transaction Test
Transaction Test Succeeded
Running Transaction
  Installing : ksh-20100621-19.el6_4.4.x86_64                               1/1 
  Verifying  : ksh-20100621-19.el6_4.4.x86_64                               1/1 
 
Installed:
  ksh.x86_64 0:20100621-19.el6_4.4                                              
 
Complete!

A note about Fedora Linux users

Type the following command to install ksh on Fedora Linux:
$ sudo dnf install ksh

How can I find out path for ksh shell?

To find out path to the ksh, type:
$ whereis ksh
OR use the grep command as follows:
$ grep --color ksh /etc/shells
Sample outputs:

/bin/ksh is now added to list of acceptable shells, verify it with the cat command:
$ cat /etc/shells
Sample outputs:

/bin/bash
/bin/csh
/bin/ksh
/bin/sh
/bin/tcsh
/bin/zsh

How do I set ksh as a default shell?

The superuser (root) may change the login shell for any account using any one of the following syntax:
$ sudo chsh -s /bin/ksh UserNameHere
OR
# chsh -s /bin/ksh UserNameHere
In this example, set default login shell to /bin/ksh for nixcraft user:
# chsh -s /bin/ksh nixcraft
Regular user can type the following command to change their shell to the ksh:
$ chsh -s /bin/ksh
Logout and login again. Verify your shell with the following command:
$ echo $SHELL
Sample outputs:

/bin/ksh

To see ksh version, type:
$ ksh --version
Sample outputs:

  version         sh (AT&T Research) 93t+ 2010-06-21

Sample ksh program

Create a file called test.ksh using a text editor:

#!/bin/ksh
# Name: test.ksh
# Purpose: My first ksh script
# Author: nixCraft <www.cyberciti.biz> under GPL v2.x+
# ------------------------------------------------------------------------
# set variables 
FILE="/etc/passwd"
NOW="$(date)"
HOSTNAME="`hostname`"
USERS_ACCOUNT="$(wc -l $FILE)"
 
# Greet user
print "Hi, $USER. I'm $0. I'm $SHELL script running on $HOSTNAME at $NOW." 
print 
print "*** User accounts: $USERS_ACCOUNT"
print "*** Current working directory: $PWD"
 
print "*** Running for loop test just for fun:"
for x in {1..3}
do
    print "Welcome $x times."
done

Save and close the file. Run it as follows:

chmod +x test.sh
./test.sh

Sample outputs:

Posted by: Vivek Gite

The author is the creator of nixCraft and a seasoned sysadmin, DevOps engineer, and a trainer for the Linux operating system/Unix shell scripting. Get the latest tutorials on SysAdmin, Linux/Unix and open source topics via RSS/XML feed or weekly email newsletter.