Commands by himanshu (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

list block devices
Shows all block devices in a tree with descruptions of what they are.

Command line calculator

Limit the cpu usage of a process
This will limit the average amount of CPU it consumes.

Batch Convert SVG to PNG (in parallel)
Use GNU Parallel: short, easy to read, and will run one job per core.

Change host name
With sed you can replace strings on the fly.

Convert seconds to [DD:][HH:]MM:SS
Converts any number of seconds into days, hours, minutes and seconds. sec2dhms() { declare -i SS="$1" D=$(( SS / 86400 )) H=$(( SS % 86400 / 3600 )) M=$(( SS % 3600 / 60 )) S=$(( SS % 60 )) [ "$D" -gt 0 ] && echo -n "${D}:" [ "$H" -gt 0 ] && printf "%02g:" "$H" printf "%02g:%02g\n" "$M" "$S" }

Uniquely (sort of) color text so you can see changes
Colorify colors input by converting the text to a number and then performing modulo 7 on it. This resulting number is used as the color escape code. This can be used to color the results of commands with complex outputs (like "482279054165371") so if any of the digits change, there's a good chance the color will change too. I say good chance because there's only 7 unique colors here, so assuming you were watching random numbers, there would be a 6/7 chance that the color would change when the number changed. This should really only be used to help quickly identify when things change, but should not be the only thing relied upon to positively assert that an output has not changed.

Add fade in/out to first & last 25 frames of a video
Replace vid.mp4 with the path to your original video file, and out.mp4 to the path where you want to save the new file. To view the output first before saving, remove "-consumer avformat:out.mp4" from the end. Documentation for mlt framework and melt command can be found here: http://www.mltframework.org/bin/view/MLT/Documentation

Notify me when users log in
Notifyme is a program that listen in background for users login, and report on login and logout. Users can be specified from a list or in a ~/notify.rc file. -C options force to display messages on the center of the screen.See man notifyme for more details. Part of notifyme package, tested on Debian.

monitor system load
Also look at xload

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: