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.
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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:
This will tell you who has the most Apache connections by IP (replace IPHERE with the actual IP you wish to check). Or if you wish, remove | grep -c IPHERE for the full list.
List top 20 IP from which TCP connection is in SYN_RECV state.
Useful on web servers to detect a syn flood attack.
Replace SYN_ with ESTA to find established connections
usefull in case of abuser/DoS attacks.
find -printf '%u\n' | sort | uniq #just users
find -printf '%g\n' | sort | uniq #just groups
Sort IP address by order
The description of how the one-liner works is here at my blog:
Greps IRC logs for phrases and lists users who said them.
shows all RPMs with files in the current directory & its subdirectories.
Ever use 'locate' to find a common phrase in a filename or directory name? Often you'll get a huge list of matches, many of which are redundant, and typically the results are not sorted. This command will 'locate' your search phrase, then show you a sorted list of just the relevant directories, with no duplications. So, for example, maybe you have installed several versions of the java jre and you want to track down every directory where files matching "java" might exist. Well, a 'locate java' is likely to return a huge list with many repeated directories since many files in one directory could contain the phrase "java". This command will whittle down the results to a minimal list of unique directory names where your search phrase finds a match.
bash/ksh subshell redirection (as file descriptors) used as input to diff
This grabs all lines that make an instantation or static call, then filters out the cruft and displays a summary of each class called and the frequency.