Feature of Unix shells and some programming languages
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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,[1] introduced with Version 7 Unix 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.
^Dahdah, Howard. "The A-Z of Programming Languages: Bourne shell, or sh, An in-depth interview with Steve Bourne, creator of the Bourne shell, or sh", Computerworld, March 5, 2009.
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In computing, commandsubstitution 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...
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shells, it supports filename wildcarding, piping, here documents, commandsubstitution, variables and control structures for condition-testing and iteration...
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expressions, and remains in use for text processing, most notably with the substitutioncommand. Popular alternative tools for plaintext string manipulation and...
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goto facility, so code restructuring may be necessary Commandsubstitution using backquotes: `command`. Here documents using << to embed a block of input...
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