how to Redirect stderr to stdout in Bash

how to Redirect stderr to stdout in Bash

how to Redirect stderr to stdout in Bash

Find out how to Redirect stderr to stdout in Bash

June 9, 2020 by Editorial Staff

Contents [hide]

• 1 Find out how to Redirect stderr to stdout in Bash
• 2 Redirecting Output #
• 3 Redirecting stderr to stdout #
• 4 Conclusion #

Find out how to Redirect stderr to stdout in Bash

We hope this post helped you to find out Find out how to Redirect stderr to stdout in Bash

When redirecting the output of a command to a file or piping it to a different command, you would possibly discover that the error messages are printed on the display.

In Bash and different Linux shells, when a program is executed, it makes use of three commonplace I/O streams. Every stream is represented by a numeric file descriptor:

• 0 – stdin, the usual enter stream.
• 1 – stdout, the usual output stream.
• 2 – stderr, the usual error stream.

A file descriptor is only a quantity representing an open file.

The enter stream gives data to this system, typically by typing within the keyboard.

This system output goes to the usual enter stream and the error messages goes to the usual error stream. By default, each enter and error streams are printed on the display.

Redirecting Output #

Redirection is a technique to seize the output from a program and ship it as enter to a different program or file.

Streams may be redirected utilizing the n> operator, the place n is the file descriptor quantity.

When n is omitted, it defaults to 1, the usual output stream. For instance, the next two instructions are the identical; each will redirect the command output (stdout) to the file.

command > file
command 1> file

To redirect the usual error (stderr) use the 2> operator:

command 2> file

You may write each stderr and stdout to 2 separate recordsdata:

command 2> error.txt 1> output.txt

To suppress the error messages from being displayed on the display, redirect stderr to /dev/null:

command 2> /dev/null

Redirecting stderr to stdout #

When saving this system’s output to a file, it’s fairly widespread to redirect stderr to stdout so to have all the things in a single file.

To redirect stderr to stdout and have error messages despatched to the identical file as commonplace output, use the next:

command > file 2>&1

> file redirect the stdout to file, and 2>&1 redirect the stderr to the present location of stdout.

The order of redirection is vital. For instance, the next instance redirects solely stdout to file. This occurs as a result of the stderr is redirected to stdout earlier than the stdout was redirected to file.

command 2>&1 > file

One other technique to redirect stderr to stdout is to make use of the &> assemble. In Bash &> has the identical that means as 2>&1:

command &> file

Conclusion #

Understanding the idea of redirections and file descriptors is essential when engaged on the command line.

To redirect stderr and stdout, use the 2>&1 or &> constructs.

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