Commands by realist (6)

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

Change size of lots of image files.
Imagemagick library is used.

Which processes are listening on a specific port (e.g. port 80)
swap out "80" for your port of interest. Can use port number or named ports e.g. "http"

Get a funny one-liner from www.onelinerz.net
Put this command in .bashrc and every time you open a new terminal a random quote will be downloaded and printed from onelinerz.net. By altering the URL in the w3m statement you can change the output: 1 to 10 lines - http://www.onelinerz.net/random-one-liners/(number)/ 20 newest lines - http://www.onelinerz.net/latest-one-liners/ Top 10 lines - http://www.onelinerz.net/top-100-funny-one-liners/ Top 10 lines are updated daily.

Get your outgoing IP address

Get AWS temporary credentials ready to export based on a MFA virtual appliance
You might want to secure your AWS operations requiring to use a MFA token. But then to use API or tools, you need to pass credentials generated with a MFA token. This commands asks you for the MFA code and retrieves these credentials using AWS Cli. To print the exports, you can use: `awk '{ print "export AWS_ACCESS_KEY_ID=\"" $1 "\"\n" "export AWS_SECRET_ACCESS_KEY=\"" $2 "\"\n" "export AWS_SESSION_TOKEN=\"" $3 "\"" }'` You must adapt the command line to include: * $MFA_IDis ARN of the virtual MFA or serial number of the physical one * TTL for the credentials

Maximum PNG compression with optipng, advpng, and advdef
optipng and advancecomp (for the the advpng and advdef tools) are the best FOSS tools for losslessly compressing PNGs. With the above tool chain, you can cut off as much as 20% off a PNG's file size.

monitor a tail -f command with multiple processes
when using named pipes only one reader is given the output by default. Also, most commands piped to by grep use a buffer which save output until tail -f finishes, which is not convenient. Here, using a combination of tee, sub-processes and the --line-buffered switch in grep we can workaround the problem.

Big (four-byte) $RANDOM
Sometimes, in a shell script, you need a random number bigger than the range of $RANDOM. This will print a random number made of four hex values extracted from /dev/urandom.

Which processes are listening on a specific port (e.g. port 80)
swap out "80" for your port of interest. Can use port number or named ports e.g. "http"

Optimal way of deleting huge numbers of files
Optimal way of deleting huge numbers of files Using -delete is faster than: $ find /path/to/dir -type f -print0 | xargs -0 rm $ find /path/to/dir -type f -exec rm {} + $ find /path/to/dir -type f -exec rm \-f {} \;


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: