If you want to use the output of one command in another command line, use command substitution. You can perform command substitution by using backticks (`) to surround a command or a dollar sign followed by parenthesis that surround a command. Surrounding a command with backticks is the older style and is being replaced by the dollar sign syntax. The output of the command can be used as an argument to another command, to set a variable, or for generating the argument list for a for loop.
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