mksh binary package in Ubuntu Focal amd64

 mksh is the successor of the Public Domain Korn shell (pdksh),
 a Bourne/POSIX compatible shell which is largely similar to the
 original AT&T Korn Shell (ksh88/ksh93).
 It includes bug fixes and feature improvements, in order to produce a
 modern, robust shell good for interactive and especially script use.
 mksh has UTF-8 support (in string operations and the Emacs editing
 mode). The code has been cleaned up and simplified, bugs fixed,
 standards compliance added, and several enhancements (for extended
 compatibility to other modern shells, as well as a couple of its
 own) are available.
 This shell is Debian Policy 10.4 compliant and works as /bin/sh on
 Debian systems (use the /bin/lksh executable) and is a good rescue
 and initrd shell (consider the /bin/mksh-static executable).
 .
 The mksh binary is a complete, full-featured shell. It provides a
 “consistent across all platforms” guarantee, using 32-bit integers
 for arithmetics, possibly deviating from POSIX.
 .
 The mksh-static binary is a version of mksh, linked against klibc,
 musl, or dietlibc (if they exist for that Debian architecture and
 are usable) and optimised for small code size, for example for use
 on initrd or initramfs images, installation or rescue systems.
 Except for omitting some features to be smaller, it is similar to
 the mksh binary otherwise. Note the exact feature set may differ
 depending on which C library was used to compile it.
 .
 The lksh binary is a script shell based on mksh intended to run old
 ksh88 and pdksh scripts, but not for interactive use. When used as
 /bin/sh it follows POSIX most closely, including use of the host’s
 “long” C data type for arithmetics. It also contains kludges so it
 can run as /bin/sh on Debian beyond what Policy dictates, to work
 around bugs in maintainer scripts and LSB init scripts shipped by
 many packages, such as including a rudimentary printf(1) builtin,
 permitting a shell function to be named stop overriding the default
 alias, more loose interpretation of shell extglobs, etc.
 .
 A sample ~/.mkshrc is included in /usr/share/doc/mksh/examples and
 provided as /etc/mkshrc conffile, which is sourced by another file
 /etc/skel/.mkshrc users are recommended to copy into their home.

Source package