# Ksh

Korn Shell (ksh) is a standard/restricted command and programming language developed by AT&T.

## Installation

First, install an implementation:

- MirBSD™ Korn Shell — Enhanced version of the public domain ksh.

  https://www.mirbsd.org/mksh.htm || mksh

- AT&T Korn shell — Official AT&T version.

  http://www.kornshell.com/ || ksh

- OpenBSDs Korn Shell — Porting of the OpenBSD version of ksh to GNU/Linux.

  http://www.connochaetos.org/oksh/ || oksh

- Public Domain Korn Shell — Clone of the AT&T Korn shell. At the moment, it has most of the ksh88 features, not much of the ksh93 features, and a number of its own features.

  http://www.cs.mun.ca/~michael/pdksh/ || pdksh

More implementations are provided by:

- obase — OpenBSD userland ported to Linux, statically linked.

  https://github.com/chneukirchen/obase || obase-git

- obase musl — OpenBSD userland ported to Linux, statically linked to musl libc.

  https://github.com/chneukirchen/obase || obase-musl-git

## Making ksh your default login shell

systemd does not implicitly make use of a shell (previously, Arch Linux init scripts were using Bash). After the boot process is complete, the default login shell is user-specified. The `chsh` command can be used to change a user's default login shell without root access if the shell is listed in `/etc/shells`. (If Ksh was installed using pacman, it should already have an entry in `/etc/shells`).

Grab the full path for Ksh using `/usr/bin/which`:

    $ which ksh

Which will probably output:

    /bin/ksh

Change the default shell for the current user:

    $ chsh -s /bin/ksh

Alternative as root, using usermod

Change the default shell using usermod:

    # usermod -s /bin/ksh username

Note: The user needs to logout and log back in, to start using Ksh as their default shell.

After logging back in, verify that Ksh is the default shell with:

    $ echo $SHELL

## Uninstallation

You must first change your default shell back to Bash before removing the Ksh package.

Change the default shell for the current user to Bash:

    $ chsh -s /bin/bash

Alternative as root, using usermod

Change the default shell using usermod:

    # usermod -s /bin/bash username

Now you can safely remove the Ksh package.

Warning: Failure to follow the above will result in all kinds of problems.

If you did not follow the above, you can still change the default shell back to Bash by editing `/etc/passwd` as root.

For example from:

    username:x:1000:1000:Full Name,,,:/home/username:/bin/ksh

to:

    username:x:1000:1000:Full Name,,,:/home/username:/bin/bash

## See also

- pdksh man page at die.net
- pdksh man page at OpenBSD

Category:

- Command shells