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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 .
PowerShell is a task automation and configuration management program from Microsoft, consisting of a command-line shell and the associated scripting language.Initially a Windows component only, known as Windows PowerShell, it was made open-source and cross-platform on August 18, 2016, with the introduction of PowerShell Core. [5]
The redirection and piping tokens can be chained together to create complex commands. For example, sort infile | uniq-c | sort-n > outfile sorts the lines of infile in lexicographical order, writes unique lines prefixed by the number of occurrences, sorts the resultant output numerically, and places the final output in outfile. [7]
The > in the third example is a redirection operator, telling the command-line interpreter to send the output of the command not to its own standard output (the screen) but to the named file. This will overwrite the file. Using >> will redirect the output and append it to the file.
Process substitution can also be used to capture output that would normally go to a file, and redirect it to the input of a process. The Bash syntax for writing to a process is >(command). Here is an example using the tee, wc and gzip commands that counts the lines in a file with wc -l and compresses it with gzip in one pass:
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Example usage of tee: The output of ls -l is redirected to tee which copies them to the file file.txt and to the pager less. The name tee comes from this scheme - it looks like the capital letter T. The tee command is normally used to split the output of a program so that it can be both displayed and saved in a file. The command can be used to ...
If you’re stuck on today’s Wordle answer, we’re here to help—but beware of spoilers for Wordle 1256 ahead. Let's start with a few hints.