I want to erase the contents of the file error.log (nginx error log file), but I don't want to actually delete the file.
is this possible?
running ubuntu
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2 Answers
74
You can use this:
>error.log
(typed just like that - an empty output redirection)
or
truncate -s0 error.log
Dennis Williamson
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@Ignacio: If the file already exists, either will truncate it. If the file doesn't exist, either will create it. – Dennis Williamson Dec 04 '10 at 03:21
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You're right, my bad. – Ignacio Vazquez-Abrams Dec 04 '10 at 03:24
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The last option worked for me, for some reason sudo >error.log didnt work for me (ubuntu 12.04) – davidkonrad May 19 '14 at 10:38
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5@davidkonrad: You would have to already be root for the redirection to work since it's performed before `sudo` takes effect. Or you can do `sudo bash -c '>error.log'` – Dennis Williamson May 19 '14 at 10:56
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OK, didnt knew that. Thank you for clarification! – davidkonrad May 19 '14 at 11:01
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The first one worked for me perfectly! Even though I dont understand what it does :D Thank you – divHelper11 Oct 25 '18 at 09:27
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1@divHelper11: In my answer I say it's an "empty output redirection". That means that "nothing" is being sent to the named file and that overwrites any existing contents. It's similar to `echo "some words" > output.txt` but nothing is going in. – Dennis Williamson Oct 25 '18 at 16:46
2
You'll confuse the daemon. Erase the file then send SIGHUP to nginx.
Ignacio Vazquez-Abrams
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SIGHUP? Can't I shut nginx down, purge the file, then start? I want to know how to erase the file for knowledge sake also. – user27449 Dec 04 '10 at 03:14
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If you wanted to, sure. But that would disrupt service. – Ignacio Vazquez-Abrams Dec 04 '10 at 03:15
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I think both a null redirection and a `truncate` are atomic, so as long as no seeking is going on (especially if the only operation that's occurring is appending) it shouldn't be disruptive. – Dennis Williamson Dec 04 '10 at 03:25