Commands by jemptymethod (5)

What's this? 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.

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Multi-thread any command
For instance: $ find . -type f -name '*.wav' -print0 |xargs -0 -P 3 -n 1 flac -V8 will encode all .wav files into FLAC in parallel. Explanation of xargs flags: -P [max-procs]: Max number of invocations to run at once. Set to 0 to run all at once [potentially dangerous re: excessive RAM usage]. -n [max-args]: Max number of arguments from the list to send to each invocation. -0: Stdin is a null-terminated list. I use xargs to build parallel-processing frameworks into my scripts like the one here:

Force GNU/Linux keyboard settings, layout and configuration
Bash snippet to force GNU/Linux keyboard settings, layout and configuration. Usefull when some GNU/Linux distributions such as *Ubuntu's store only limited configation options due to demonstration purposes on LiveUSB or Live persistent devices. Overcomes the English QWERTY to French AZERTY settings failure. Code bash en ligne de commande pour forcer l'adoption du clavier AZERTY sur les cl? USB bootable en Ubuntu.

Print all lines between two line numbers
Print all lines between two line numbers This command uses sed(1) to print all lines between two known line numbers in a file. Useful for seeing output in a log file, where the line numbers are known. The above command will print all lines between, and including, lines 3 and 6.

Random colours at random locations

Print the IPv4 address of a given interface

draw line separator
Even shorter: $ seq -s '*' 120|tr -d '[0-9]'

Unzip and untar a *.tar.gz file in one go to a specific directory
A *.tar.gz file needs to be unzipped & then untarred. Previously I might have unzipped first with $gunzip -d file.tar.gz and then untarred the result with $tar -xvf file.tar (Options are extract, verbose, file) Using the -z (decompress) option on tar avoids the use of gzip (or gunzip) first. Additionally the -C option will specify the directory to extract to.

Find last reboot time
Specific to OSX.

Summarise the size of all files matching a simple regex
Use the find command to match certain files and summarise their total size in KBytes.

Count opening and closing braces in a string.
This function counts the opening and closing braces in a string. This is useful if you have eg long boolean expressions with many braces and you simply want to check if you didn't forget to close one.

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.


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,…):

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