Linux

7.4    Input and Output Redirection

When you run commands in bash, there are three standard files. The term file can cause a little confusion here. These are not actually real files, but file descriptors that are treated like files at the operating system level:

• Standard inputThe currently executing program, such as bash or any command started from there, reads all input from standard input. If you work interactively in a terminal window, then the keyboard is considered the default input source.

• Standard outputThe entire output of the program is directed here—for example, the listing of all files via ls. Usually, the terminal window is the standard output.

• Standard errorsError messages are also usually displayed in the current terminal. ...