Null a file with sudo

sudo bash -c "> /var/log/httpd/access_log"

2
By: zlemini
2014-10-02 15:39:47

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What Others Think

time for i in {1..1000} ; do bash -c "> /tmp/somefile"; done real 0m10.800s user 0m0.032s sys 0m0.100s time for i in {1..1000} ; do cat /dev/null >/tmp/somefile; done real 0m9.932s user 0m0.040s sys 0m0.080s time for i in {1..1000} ; do echo -n > /tmp/somefile ; done real 0m0.010s user 0m0.004s sys 0m0.004s
pdxdoughnut · 197 weeks and 4 days ago
Speed isn't what i was aiming for, just the ability to null a file owned by root etc. - without having to switch to root. You are running tests without sudo, if you run them with sudo its a lot closer.
zlemini · 197 weeks and 4 days ago
The reason I test for speed is that people who find ideas here often use them in places we didn't think of. Many of those places are inside large for/while loops where a little time really adds up. And frankly, I was surprised at how big of a difference there was in these two (or three) methods.
pdxdoughnut · 197 weeks and 1 day ago
This is what you should compare: time for i in {1..1000} ; do echo -n > /tmp/somefile ; done real 0m0.053s user 0m0.027s sys 0m0.025s time for i in {1..1000} ; do > /tmp/somefile; done real 0m0.048s user 0m0.022s sys 0m0.025s But the command is useful to null a file using sudo, if for example /tmp/somefile was owned by root and you wanted to truncate it without switching to root first.
zlemini · 197 weeks ago
You are absolutely correct.
pdxdoughnut · 197 weeks ago

What do you think?

Any thoughts on this command? Does it work on your machine? Can you do the same thing with only 14 characters?

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