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.
» http://twitter.com/commandlinefu
» http://twitter.com/commandlinefu3
» http://twitter.com/commandlinefu10
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:
Great idea camocrazed. Another twist would be to display a different man page based on the day of the year. The following will continuously cycle through all man pages:
man $(ls /bin | sed -n $(($(date +%j) % $(ls /bin | wc -l)))p)
Of course, the httpd can be replaced with any other process name
Thanks to flatcap for optimizing this command.
This command takes advantage of the ext4 filesystem's resistance to fragmentation.
By using this command, files that were previously fragmented will be copied / deleted / pasted essentially giving the filesystem another chance at saving the file contiguously. ( unlike FAT / NTFS, the *nix filesystem always try to save a file without fragmenting it )
My command only effects the home directory and only those files with your R/W (read / write ) permissions.
There are two issues with this command:
1. it really won't help, it works, but linux doesn't suffer much (if any ) fragmentation and even fragmented files have fast I/O
2. it doesn't discriminate between fragmented and non-fragmented files, so a large ~/ directory with no fragments will take almost as long as an equally sized fragmented ~/ directory
The benefits i managed to work into the command:
1. it only defragments files under 16mb, because a large file with fragments isn't as noticeable as a small file that's fragmented, and copy/ delete/ paste of large files would take too long
2. it gives a nice countdown in the terminal so you know how far how much progress is being made and just like other defragmenters you can stop at any time ( use ctrl+c )
3. fast! i can defrag my ~/ directory in 11 seconds thanks to the ramdrive powering the command's temporary storage
bottom line:
1. its only an experiment, safe ( i've used it several times for testing ), but probably not very effective ( unless you somehow have a fragmentation problem on linux ). might be a placebo for recent windows converts looking for a defrag utility on linux and won't accept no for an answer
2. it's my first commandlinefu command
Find the source file which contains most number of lines in your workspace
:)
This function counts the opening and closing braces in a string. This is useful if you have eg long boolean expressions with many braces and you simply want to check if you didn't forget to close one.
We use `-not -name ".*"` for the reason we must omit hidden files (which unnecessary). We can only show up total lines like this:
find * -type f -not -name ".*" | xargs wc -l | tail -1
The same as the other two alternatives, but now less forking! Instead of using '\;' to mark the end of an -exec command in GNU find, you can simply use '+' and it'll run the command only once with all the files as arguments.
This has two benefits over the xargs version: it's easier to read and spaces in the filesnames work automatically (no -print0). [Oh, and there's one less fork, if you care about such things. But, then again, one is equal to zero for sufficiently large values of zero.]
If you use HISTTIMEFORMAT environment e.g. timestamping typed commands, $(echo "1 2 $HISTTIMEFORMAT" | wc -w)
gives the number of columns that containing non-command parts per lines.
It should universify this command.
find -exec is evil since it launches a process for each file. You get the total as a bonus.
Also, without -n sort will sort by lexical order (that is 9 after 10).
Another way of counting the line output of tail over 10s not requiring pv.
Cut to have the average per second rate :
tail -n0 -f access.log>/tmp/tmp.log & sleep 10; kill $! ; wc -l /tmp/tmp.log | cut -c-2
You can also enclose it in a loop and send stderr to /dev/null :
while true; do tail -n0 -f access.log>/tmp/tmp.log & sleep 2; kill $! ; wc -l /tmp/tmp.log | cut -c-2; done 2>/dev/null
Gives you a nice quick summary of how many lines each of your files is comprised of. (In this example, we just check .c, .h, .php and .pl). Since we just use wc -l to count, you'll just get a very rough estimate of how many lines of actual code there are. Use a more sophisticated algorithm instead if you need to.
I created this command to give me a quick overview of how many file types a directory, and all its subdirectories, contains. It works based off file extension, rather than file(1)'s magic output, because it ended up being more accurate and less confusing.
Files that don't have an ext (README) are generally not important for me to want to count, but you're free to customize this fit your needs.
A command to find out what the day ends in. Can be edited slightly to find out what "any" output ends in.
NB: I haven't tested with weird and wonderful output.
extension to tali713's random fact generator. It takes the output & sends it to notify-osd. Display time is proportional to the lengh of the fact.
Finds all C++, Python, SWIG files in your present directory (uses "*" rather than "." to exclude invisibles) and counts how many lines are in them. Returns only the last line (the total).
This command will output the total number of files in a SVN Repository.
Usefull if you want to check if something is applying a dictonary of brute force.
There is a limit to how many processes you can run at the same time for each user, especially with web hosts. If the maximum # of processes for your user is 200, then the following sets OPTIMUM_P to 100.
OPTIMUM_P=$(( (`ulimit -u` - `find /proc -maxdepth 1 \( -user $USER -o -group $GROUPNAME \) -type d|wc -l`) / 2 ))
This is very useful in scripts because this is such a fast low-resource-intensive (compared to ps, who, lsof, etc) way to determine how many processes are currently running for whichever user. The number of currently running processes is subtracted from the high limit setup for the account (see limits.conf, pam, initscript).
An easy to understand example- this searches the current directory for shell scripts, and runs up to 100 'file' commands at the same time, greatly speeding up the command.
find . -type f | xargs -P $OPTIMUM_P -iFNAME file FNAME | sed -n '/shell script text/p'
I am using it in my http://www.askapache.com/linux-unix/bash_profile-functions-advanced-shell.html especially for the xargs command. Xargs has a -P option that lets you specify how many processes to run at the same time. For instance if you have 1000 urls in a text file and wanted to download all of them fast with curl, you could download 100 at a time (check ps output on a separate [pt]ty for proof) like this:
cat url-list.txt | xargs -I '{}' -P $OPTIMUM_P curl -O '{}'
I like to do things as fast as possible on my servers. I have several types of servers and hosting environments, some with very restrictive jail shells with 20processes limit, some with 200, some with 8000, so for the jailed shells my xargs -P10 would kill my shell or dump core. Using the above I can set the -P value dynamically, so xargs always works, like this.
cat url-list.txt | xargs -I '{}' -P $OPTIMUM_P curl -O '{}'
If you were building a process-killer (very common for cheap hosting) this would also be handy.
Note that if you are only allowed 20 or so processes, you should just use -P1 with xargs.
This makes an alias for a command named 'busy'. The 'busy' command opens a random file in /usr/include to a random line with vim. Drop this in your .bash_aliases and make sure that file is initialized in your .bashrc.