In computing, command substitution is a facility that allows a command to be run and its output to be pasted back on the command line as arguments to another command. Command substitution first appeared in the Bourne shell, introduced with Unix 7th Edition in 1979, and has remained a characteristic of all later Unix shells. The feature has since been adopted in other programming languages as well, including Perl, PHP, Ruby and Microsoft's Powershell under Windows. It also appears in Microsoft's CMD.EXE in the FOR command and the ( ) command.