As well as using the shell to run commands you can use its built-in programming language to write your own commands or programs. You can put commands into a file - known as a shell script - and then execute that file as you would a command or program. The use of the Bourne shell (sh) is illustrated as this is available on all UNIX systems. ... The C and TC shells use a programming language which is similar to the C programming language. Creating and executing simple shell scripts . ...