Commands by unixmonkey12364 (1)

What's this?

commandlinefu.com 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


Check These Out

Displays the attempted user name, ip address, and time of SSH failed logins on Debian machines
A variation of a script I found on this site and then slimmed down to just use awk. It displays all users who have attempted to login to the box and failed using SSH. Pipe it to the sort command to see which usernames have the most failed logins.

RTFM function
Sometimes you don't have man pages only '-h' or '--help'.

Empty a file

Print number of mb of free ram
Here we instead show a more real figure for how much free RAM you have when taking into consideration buffers that can be freed if needed. Unix machines leave data in memory but marked it free to overwrite, so using the first line from the "free" command will mostly give you back a reading showing you are almost out of memory, but in fact you are not, as the system can free up memory as soon as it is needed. I just noticed the free command is not on my OpenBSD box.

Grep all non-ascii character in file
It will highlight non-ascii character in a file. those character can cause problem for some application parsing ascii file.

restore the contents of a deleted file for which a descriptor is still available
Note that the file at the given path will have the contents of the (still) deleted file, but it is a new file with a new node number; in other words, this restores the data, but it does not actually "undelete" the old file. I posted a function declaration encapsulating this functionality to http://www.reddit.com/r/programming/comments/7yx6f/how_to_undelete_any_open_deleted_file_in_linux/c07sqwe (please excuse the crap formatting).

Turns hidden applications transparent in the Mac OS X dock.
In Mac OS X, pressing Command+H will hide an application. While that application's windows vanish, there is no other visual feedback, meaning there is no immediate distinction between an application running with no windows open and a hidden application. This command turns hidden applications' icons transparent, providing a clear and obvious distinction. Change YES to NO to restore the previous functionality.

do something else while waiting for an event, such as reboot
until (ssh root@10.1.1.39 2> /dev/null); do date; sleep 15; done In this case will execute "date" then "sleep 15" until we are able to ssh into server, such as after a reboot Could also be like: until ( ping 10.1.1.39 1> /dev/null); do echo "server 10.1.1.39 is down"; sleep 15; done

Limit the cpu usage of a process
Similar to `cpulimit`, although `prlimit` can be found shipped with recent util-linux. Example: limit CPU consumption to 10% for a math problem which ordinarily takes up 100% CPU: Before: $ bc -l

coloured shell prompt
This coloured prompt will show: username in green, grey "@" sign, hostname in red, current directory in yellow, typed commands in green.


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.

» http://twitter.com/commandlinefu
» http://twitter.com/commandlinefu3
» http://twitter.com/commandlinefu10

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: