Linux Command Line - I/O Redirection

Streams

• 0, stdin is standard input.
• 1, stdout is standard output.
• 2, stderr is standard error.

Standard Input

Transmitted through the keyboard, from the user to a program. It is terminated when the end of file (EOF) is reached.

Standard Output

Display data generated by a program on the terminal if it is not redirected.

Standard Error

Display errors generated by a program on the terminal if it is not redirected.

Overwrite Target

• >, 1> standard output.
• < standard input.
• 2> standard error.
• &> standard output and standard error.
• i>&j redirect anything that targets i to j.
• 2>&1 standard error to standard output

Append Target

• >>, 1>> standard output.
• << standard input.
• 2>> standard error.

Pipes

Redirect streams from one program to another.

Filters

Alter piped redirection and output: find, grep, tee, tr, wc.

/dev/null special file that trashes any data that it receives. You can redirect output that you do not want displayed or passed to another program.