Terminal GuideKsh
Korn Shell
Powerful shell combining features of sh and csh, popular in enterprise
Overview
The Korn Shell (ksh) was developed by David Korn at Bell Labs in 1983. It combines the best features of the Bourne shell and C shell, adding many improvements. Ksh is the default shell on many commercial Unix systems like AIX, HP-UX, and Solaris.
Quick Facts
| Full Name | Korn Shell |
| Category | Specialized |
| POSIX Compliant | Yes |
| Config File | .kshrc |
| Default On | AIX, HP-UX, Solaris |
| First Release | 1983 |
Who Should Use Ksh?
- Enterprise Unix users - Default on AIX, HP-UX, Solaris
- Legacy system admins - Maintaining existing ksh scripts
- Advanced scripters - Powerful scripting features
- POSIX-plus needs - POSIX with useful extensions
Installation
Install Korn Shell on various systems.
# Install on macOS
brew install ksh
# Install on Debian/Ubuntu
sudo apt install ksh
# Install on Fedora
sudo dnf install ksh
# Install ksh93 (original AT&T version)
# Now open source at https://github.com/ksh93/ksh
# Set as default shell
chsh -s $(which ksh)Basic Usage
Ksh scripting features.
#!/bin/ksh
# Variables with types
typeset -i num=42 # Integer
typeset -l lower="ABC" # Lowercase
echo "$lower" # abc
# Associative arrays (ksh93)
typeset -A colors
colors[red]="#FF0000"
colors[green]="#00FF00"
echo "${colors[red]}"
# Coprocesses
cmd |&
read -p line # Read from coprocess
# Built-in arithmetic
(( result = 5 + 3 ))
echo "$result"
# Pattern matching
[[ "hello" == h* ]] && echo "Match!"Configuration
Ksh configuration files.
# ~/.kshrc - Interactive shell configuration
# Set ENV to point to this file in ~/.profile:
# export ENV=~/.kshrc
# Custom prompt
PS1='$(whoami)@$(hostname):$(pwd)$ '
# Aliases
alias ll='ls -la'
alias h='fc -l' # History
# Enable vi mode (default) or emacs mode
set -o vi
# set -o emacs
# History settings
HISTSIZE=1000
HISTFILE=~/.ksh_historyKey Features
Associative Arrays
Hash tables built into the shell (ksh93)
Floating Point
Native floating-point arithmetic support
Coprocesses
Two-way communication with background processes
Discipline Functions
Custom getter/setter for variables
FAQ
What is the difference between ksh88 and ksh93?
ksh93 added many features including associative arrays, floating-point math, and compound variables. ksh88 is older but still common on legacy systems.
Is ksh still relevant today?
Yes, especially in enterprise Unix environments. Many critical systems run ksh scripts, and ksh93 is now open source and actively maintained.
Summary
Key takeaways for Ksh:
- Default shell on commercial Unix systems (AIX, HP-UX, Solaris)
- Advanced features like associative arrays and floating-point math
- Excellent backward compatibility with Bourne shell
- Now open source (ksh93)
Official Documentation
For authoritative information, refer to the official documentation: