Complete KornShell (ksh) Cheatsheet

Quick Reference

KornShell (ksh) is a Unix shell developed by David Korn at Bell Labs, combining features of Bourne shell and C shell.

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Navigation 4 Variables 6 Arrays 5 History 5 Job Control 4 Scripting 8 Keyboard Shortcuts 10

Change directory

cd /usr/local # Change to /usr/local
cd ~ # Change to home directory
cd - # Switch to previous directory

dirs

Show directory stack (ksh93+)

dirs # Show directory stack
dirs -v # Show with numbers

pushd, popd

Manipulate directory stack (ksh93+)

pushd /usr/local # Add to stack and cd
pushd +1 # Rotate stack
popd # Return to previous directory

pwd -P

Print physical directory (without symlinks)

pwd -P # Show actual path
pwd -L # Show with symlinks (default)

2 Variables

variable=value

Set shell variables

name="John"
count=10
files=$(ls) # Command substitution

export

Set environment variables

export PATH="/usr/local/bin:$PATH"
export EDITOR=vim
export -p # List all exported variables

unset

Remove variables

unset name # Remove variable
unset -f function_name # Remove function

Special variables

Predefined shell variables

$HOME # Home directory
$PATH # Executable search path
$? # Exit status of last command
$$ # Current process ID
$# # Number of arguments
$0 # Script name

Variable expansion

Advanced variable manipulation

${var:-default} # Use default if unset
${var#prefix} # Remove prefix
${var%suffix} # Remove suffix
${var//old/new} # Replace all occurrences

typeset

Declare variable attributes

typeset -i count # Integer variable
typeset -r PI=3.14 # Read-only variable
typeset -x VAR # Export variable
typeset -f # List functions

3 Arrays

set -A

Create indexed array (ksh88)

set -A colors red green blue
echo ${colors[1]} # green

array=(...)

Create indexed array (ksh93+)

colors=(red green blue)
files=(*.txt) # All .txt files

Associative arrays

Key-value pairs (ksh93+)

typeset -A person
person[name]="John"
person[age]=30
echo ${person[name]} # John

Array operations

Working with array elements

${array[*]} # All elements
${#array[*]} # Number of elements
${!array[*]} # All indices/keys
${array[@]:1:2} # Slice (elements 1-2)

Compound variables

Complex data structures (ksh93+)

typeset -C point=(x=10 y=20)
echo $point.x # 10
point.z=30 # Add new field

4 History

history

View command history

history # Show all commands
history 10 # Show last 10 commands
fc -l # Alternative to history

!! and !-n

Re-execute previous commands

!! # Repeat last command
!-2 # Repeat command 2 back
!string # Last command starting with 'string'

Fix command (edit and re-run)

fc # Edit last command in $EDITOR
fc -l 100 105 # List commands 100-105
fc -s old=new # Substitute in last command

HISTFILE and HISTSIZE

Configure history behavior

HISTFILE=~/.ksh_history
HISTSIZE=1000
HISTCONTROL=ignoredups # Ignore duplicates

Repeat command (ksh93+)

r # Repeat last command
r vi # Repeat last vi command
r -2 # Repeat command 2 back

5 Job Control

jobs

List background jobs

jobs # List jobs
jobs -l # List with PIDs

&, bg, fg

Background and foreground jobs

long_command & # Run in background
Ctrl+Z # Suspend current job
bg %1 # Resume job 1 in background
fg %2 # Bring job 2 to foreground

kill

Terminate processes

kill %1 # Kill job 1
kill -9 1234 # Force kill PID 1234
kill -l # List signals

disown

Remove job from shell's job table

disown %1 # Remove job 1
disown -a # Remove all jobs

6 Scripting

Shebang

Ksh script header

#!/bin/ksh
#!/usr/bin/env ksh

Conditionals

If-then-else statements

if [[ $user == "root" ]]; then
  echo "You are root"
elif [[ $user == "admin" ]]; then
  echo "You are admin"
else
  echo "You are $user"
fi

Loops

For and while loops

# For loop
for color in red green blue; do
  echo $color
done

# While loop
count=1
while (( count <= 5 )); do
  echo "Count: $count"
  (( count++ ))
done

Case statement

Pattern matching conditional

case $choice in
  start)
    echo "Starting..."
    ;;
  stop)
    echo "Stopping..."
    ;;
  *)
    echo "Unknown option"
    ;;
esac

Functions

Define reusable code blocks

function greet {
echo "Hello, $1"
}
greet "World" # Hello, World

Arithmetic

Numeric operations

(( sum = 5 + 3 ))
(( count++ ))
(( result = (x * y) / z ))
echo "Sum is $sum"

Command line args

Handling script arguments

# script.ksh arg1 arg2
echo "Script: $0"
echo "First arg: $1"
echo "All args: $@"
echo "Arg count: $#"

getopts

Process command-line options

while getopts ":a:b:" opt; do
  case $opt in
    a) arg_a=$OPTARG;;
    b) arg_b=$OPTARG;;
    \?) echo "Invalid option: -$OPTARG";;
  esac
done

7 Keyboard Shortcuts

Editing shortcuts

Command line editing

Ctrl+A # Move to beginning of line
Ctrl+E # Move to end of line
Ctrl+K # Delete to end of line
Ctrl+U # Delete to beginning of line
Ctrl+W # Delete previous word

Completion

File and command completion

Esc, Esc # Complete filename
Ctrl+D # List possible completions
Tab # Complete command (if set)

History navigation

Browse command history

Up/Down # Navigate history
Ctrl+P # Previous command
Ctrl+N # Next command
Ctrl+R # Reverse search

Process control

Manage running processes

Ctrl+C # Interrupt process
Ctrl+Z # Suspend process
Ctrl+D # End of input (logout)
Ctrl+S # Pause output
Ctrl+Q # Resume output