Wiki

This page is read only. You can view the source, but not change it. Ask your administrator if you think this is wrong.

====== BASH - Output - Understand the difference between standard output and standard error ======

A sane command writes the output that you request to standard output (stdout) and only writes errors to standard error (stderr).

For example:

<code bash>
dig +short A wiki.sharewiz.net
5.42.134.35

ip=$(dig +short A wiki.sharewiz.net)
echo "{$ip}"
{5.42.134.35}

ls no-such-file
ls: cannot access 'no-such-file': No such file or directory

output=$(ls no-such-file)
ls: cannot access 'no-such-file': No such file or directory

echo "{$output}"
{}
</code>

<WRAP info>
**NOTE:**  In this example:

  * **dig** wrote output to stdout, which was also captured in the **ip** variable.
  * This was all successful.

  * **ls** encountered an error, so it did not write anything to stdout.
  * It wrote to stderr, which was not captured (because we **2>&1** was not used).
  * The error message appeared directly on the terminal instead.

</WRAP>

----