Introduction

The command line, is a text-based interface which allows for interaction with the computer and execution of commands. The actual command interpreter which carries out the commands is referred to as the shell and there are multiple examples of shells such as bash, zsh, sh, etc.

Input and Output Redirection

It is possible to redirect input and output from and to files when invoking commands:

Redirection	Description
`< in_file`	Redirect `in_file` into the command's standard input.
`> out_file`	Redirect the command's standard output into `out_file` by overwriting it.
`>> out_file`	Redirect the command's standard output into `out_file` by appending to it.
`> err_file`	Redirect the command's standard error into `err_file` by overwriting it.
`>> err_file`	Redirect the command's standard error into `err_file` by appending to it.

Pipes

Moreover, information may be redirected directly from one command to another by using unnamed pipes (|).