What is command substitution in operating systems?

Command substitution is a powerful feature in operating systems that allows the output of one command to be captured and used as an argument in another command. This functionality enhances the versatility of command-line operations by enabling you to create dynamic command structures where the output of one command directly informs the behavior of another.

For example, if you want to pass the result of a file search to another command that processes that file, command substitution allows you to do this seamlessly. You can encapsulate a command within specific syntax, such as backticks (`command`) or the more modern syntax using dollar sign and parentheses ($(command)), to achieve this. When the first command is executed, its output replaces the command substitution syntax in the command line.

This feature is essential for automation and scripting, as it allows for more complex operations to be performed without requiring manual intervention. It enables users to build more efficient and succinct command-line expressions, streamlining workflow and enhancing productivity.