Null a file with sudo

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

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

1 Alternatives + Submit Alt

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 · 364 weeks and 1 day 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 · 364 weeks and 1 day 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 · 363 weeks and 4 days 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 · 363 weeks and 4 days ago
You are absolutely correct.
pdxdoughnut · 363 weeks and 4 days 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?

You must be signed in to comment.

What's this? is the place to record those command-line gems that you return to again and again. That way others can gain from your CLI wisdom and you from theirs too. All commands can be commented on, discussed and voted up or down.

Share Your Commands

Stay in the loop…

Follow the Tweets.

Every new command is wrapped in a tweet and posted to Twitter. Following the stream is a great way of staying abreast of the latest commands. For the more discerning, there are Twitter accounts for commands that get a minimum of 3 and 10 votes - that way only the great commands get tweeted.


Subscribe to the feeds.

Use your favourite RSS aggregator to stay in touch with the latest commands. There are feeds mirroring the 3 Twitter streams as well as for virtually every other subset (users, tags, functions,…):

Subscribe to the feed for: