Command Line Redirection

Gregg

July 8, 2023

Redirection is very significant in shell scripting. It provides you a means to save the output of a command to a file or multiple files (one for stdout and one for stderr).

Below is a table of simple redirections that are the most useful in shell scripting. Here we are using the following naming conventions:

stdout – The output of the script/command
stderr – The errors generated by the script/command
outfile – A target filename where you wish to store the output
errfile – A target filename where you wish to store the errors

Command Description/Purpose

command 2>errfile Redirect stderr to errfile

command >outfile 2>errfile Redirect stderr to file named errfile and stdout to file named outfile

command &> outfile Redirect stderr and stdout to outfile

command 2>&- Just suppress error messages. No file created. No error message displayed on screen

command 2>&1 Redirect error messages to standard output. Useful in shell script when you need to forcefully display error messages on screen

Command	Description/Purpose
command 2>errfile	Redirect stderr to errfile
command >outfile 2>errfile	Redirect stderr to file named errfile and stdout to file named outfile
command &> outfile	Redirect stderr and stdout to outfile
command 2>&-	Just suppress error messages. No file created. No error message displayed on screen
command 2>&1	Redirect error messages to standard output. Useful in shell script when you need to forcefully display error messages on screen