Last checked against version &bash-contversion;. bash is the Bourne-Again SHell, which is a widely used command interpreter on Unix systems. The bash program reads from standard input (the keyboard). A user types something and the program will evaluate what he has typed and do something with it, like running a program. bashbug is a shell script to help the user compose and mail bug reports concerning bash in a standard format. sh is a symlink to the bash program. When invoked as sh, bash tries to mimic the startup behavior of historical versions of sh as closely as possible, while conforming to the POSIX standard as well.