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:
See who is using a specific port. Especially when you're using AIX. In Ubuntu, for example, this can easily be seen with the netstat command.
You can use only awk
Detect duplicate UID in you /etc/passwd (or GID in /etc/group file).
Duplicate UID is often forbidden for it can be a security breach.
count connections, group by IP and port
Reads stdin, and outputs each line only once - without sorting ahead of time. This does use more memory than your system's sort utility.
... plus do a sort according frequency
A shorter version
Works on current directory, with built-in sorting.
list top committers (and number of their commits) of svn repository.
in this example it counts revisions of current directory.
Gives the same results as the command by putnamhill using nine less characters.
All with only one pipe. Should be much faster as well (sort is slow). Use find instead of ls for recursion or reliability.
Edit: case insensitive
If we want files with more than one extension, like .tar.gz, only appear the latest, .gz:
ls -Xp /path/to/dir | grep -Eo "\.[^./]+$" | uniq
If your grep doesn't have an -o option, you can use sed instead.
Just a little simplification.
Once you get into advanced/optimized scripts, functions, or cli usage, you will use the sort command alot. The options are difficult to master/memorize however, and when you use sort commands as much as I do (some examples below), it's useful to have the help available with a simple alias. I love this alias as I never seem to remember all the options for sort, and I use sort like crazy (much better than uniq for example).
# Sorts by file permissions
find . -maxdepth 1 -printf '%.5m %10M %p\n' | sort -k1 -r -g -bS 20%
00761 drwxrw---x ./tmp
00755 drwxr-xr-x .
00701 drwx-----x ./askapache-m
00644 -rw-r--r-- ./.htaccess
# Shows uniq history fast
history 1000 | sed 's/^[0-9 ]*//' | sort -fubdS 50%
exec bash -lxv
use Linux ;)
Counts TCP states from Netstat and displays in an ordered list.
The cut should match the relevant timestamp part of the logfile, the uniq will count the number of occurrences during this time interval.
Change the cut range for hits per 10 sec, minute and so on... Grep can be used to filter on url or source IP.
awk is evil!