commandlinefu.com is the place to record those command-line gems that you return to again and again.
Delete that bloated snippets file you've been using and share your personal repository with the world. 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.
If you have a new feature suggestion or find a bug, please get in touch via http://commandlinefu.uservoice.com/
You can sign-in using OpenID credentials, or register a traditional username and password.
First-time OpenID users will be automatically assigned a username which can be changed after signing in.
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.
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:
I needed a way to search all files in a web directory that contained a certain string, and replace that string with another string. In the example, I am searching for "askapache" and replacing that string with "htaccess". I wanted this to happen as a cron job, and it was important that this happened as fast as possible while at the same time not hogging the CPU since the machine is a server.
So this script uses the nice command to run the sh shell with the command, which makes the whole thing run with priority 19, meaning it won't hog CPU processing. And the -P5 option to the xargs command means it will run 5 separate grep and sed processes simultaneously, so this is much much faster than running a single grep or sed. You may want to do -P0 which is unlimited if you aren't worried about too many processes or if you don't have to deal with process killers in the bg.
Also, the -m1 command to grep means stop grepping this file for matches after the first match, which also saves time.
This pipeline will find, sort and display all files based on mtime. This could be done with find | xargs, but the find | xargs pipeline will not produce correct results if the results of find are greater than xargs command line buffer. If the xargs buffer fills, xargs processes the find results in more than one batch which is not compatible with sorting.
Note the "-print0" on find and "-0" switch for perl. This is the equivalent of using xargs. Don't you love perl?
Note that this pipeline can be easily modified to any data produced by perl's stat operator. eg, you could sort on size, hard links, creation time, etc. Look at stat and just change the '9' to what you want. Changing the '9' to a '7' for example will sort by file size. A '3' sorts by number of links....
Use head and tail at the end of the pipeline to get oldest files or most recent. Use awk or perl -wnla for further processing. Since there is a tab between the two fields, it is very easy to process.
A little bit smaller, faster and should handle files with special characters in the name.
Based on the MrMerry one, just add some visuals and sort directory and files
use the locate command to find files on the system and verify they exist (-e) then display each one in full details.
xargs -P N spawns up to N worker processes. -n 40 means each grep command gets up to 40 file names each on the command line.
By putting the "-not \( -name .svn -prune \)" in the very front of the "find" command, you eliminate the .svn directories in your find command itself. No need to grep them out.
You can even create an alias for this command:
alias svn_find="find . -not \( -name .svn -prune \)"
Now you can do things like
svn_find -mtime -3
only installed apps: /^ii/!d
avoiding current kernel stuff: /'"$(uname -r | sed "s/\(.*\)-\([^0-9]\+\)/\1/")"'/d
using app names: s/^[^ ]* [^ ]* \([^ ]*\).*/\1/
avoiding stuff without a version number: /[0-9]/!d
In the example, uid 0 is root. foo:foo are the user:group you want to make owner and group. '.' is the "current directory and below." -print0 and -0 indicate that filenames and directories "are terminated by a null character instead of by whitespace."
This will, for an application that has already been removed but had its configuration left behind, purge that configuration from the system. To test it out first, you can remove the last -y, and it will show you what it will purge without actually doing it. I mean it never hurts to check first, "just in case." ;)
If you're like me and want to keep all your music rated, and you use xmms2, you might like this command.
I takes 10 random songs from your xmms2 library that don't have any rating, and adds them to your current playlist. You can then rate them in another xmms2 client that supports rating (I like kuechenstation).
I'm pretty sure there's a better way to do the grep ... | sed ... part, probably with awk, but I don't know awk, so I'd welcome any suggestions.
Lists the local files that are not present in the remote repository (lines beginning with ?)
and add them.
By time thumbnail images in ~/thumbnails take up too much space, this command will help deleting old ones.
Find options explained:
-type f : find files only, not directories
-atime +30 : last accessed more than 30 days ago
Can be used for other commands as well, replace rm with ls.
It is easy to make this shorter but if the filenames involved have spaces, you will need to do use find's "-print0" option in conjunction with xargs's "-0" option. Otherwise the shell that xargs uses to execute the "rm" command line will treat the space as a token separator, thereby treating the name as two (or more) names.
Run this in the directory you store your music in.
mp3gain and vorbisgain applies the ReplayGain normalization routine to mp3 and ogg files (respectively) in a reversible way.
ReplayGain uses psychoacoustic analysis to make all files sound about the same loudness, so you don't get knocked out of your chair by loud songs after cranking up the volume on quieter ones.