Here's a simple one. How do I truncate an existing file in linux? That is, how do I empty the contents of the file but keep the file. I can always delete the file then touch it but I was wondering if there's a single command that'll get the job done.
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HopelessN00b
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pygorex1
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6 Answers
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>output-file -- shortest possible version.
womble
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1accepted for shortness - btw what does the extra colon do in `:>output-file` ? – pygorex1 Dec 02 '09 at 21:06
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No idea; probably best to ask mezgani since he was the one who suggested it. – womble Dec 02 '09 at 21:26
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colon's a `noop` – Jé Queue Dec 02 '09 at 21:29
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This is the only correct answer. – Dennis Williamson Dec 02 '09 at 21:42
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@Xepoch: Thanks; I couldn't find it mentioned in `bash`(1), it's too common a character. I suspected it was something like that, though. – womble Dec 02 '09 at 22:06
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This solution is more efficient than cat, because it doesn't create a subprocess (in addition to the shell process):
true >output-file
pts
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You may do easy :)
:>output-file
Ali Mezgani
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This is short and it works in all major shells I use (bash, dash, zsh, pdksh, tcsh). – pts Dec 02 '09 at 22:31
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There is also:
truncate --size 0 file
Available from gnu coreutils (and probably others too).
I think it reads better than >file, and truncate also have more options (see truncate --help).
Ezbob
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I'm sure a harder-core *nix person will have a better idea, but I've always done:
cat /dev/null > output-file
To truncate files.
Evan Anderson
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echo -n > YOURFILE
will remove file contents and keep the file, structure and permission intact.