Commands by symgryph (9)

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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download a sequence of vim patch
Seq allows you to define printf like formating by specified with -f, %03g is actually tells seq I got three digits, fill the blank digits with 0, and the range is from 176 to 240.

Rename files in batch

Test I/O performance by timing the writing of 100Mb to disk
Write 200 blocks of 512k to a dummy file with dd, timing the result. The is useful as a quick test to compare the performance of different file systems.

encode a text to url_encoded format
usefull for posts via wget

Suspend, background, and foreground a process
1. Start a process, such as 'top' command 2. # suspend process {ctrl-Z} 3. # background process bg 4. # list all backgrounded jobs jobs 5. # bring it back to foreground fg

Detect illegal access to kernel space, potentially useful for Meltdown detection
Based on capsule8 agent examples, not rigorously tested

Want to known what time is it in another part of the world ?
available timezone can be found in /usr/share/zoneinfo. Other examples: $ TZ=Europe/Paris date; TZ=Australia/Sydney date; TZ=America/New_York date this is based on zoneinfo files on macosx. Your mileage my vary on other unix dialects

count of files from each subfolder
Find the number of files from each folder

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" }

How to copy CD/DVD into hard disk (.iso)
A dear friend of mine asked me how do I copy a DVD to your hard drive? If you want to make a copy of the ISO image that was burned to a CD or DVD, insert that medium into your CD/DVD drive and (assuming /dev/cdrom is associated with your computer?s CD drive) type the following command

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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.


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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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