Commands by jedahan (4)

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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Display Spinner while waiting for some process to finish
alternatively, run the spinner for 5 seconds: timeout 5 bash -c 'spinner=( Ooooo oOooo ooOoo oooOo ooooO oooOo ooOoo oOooo); while true; do for i in ${spinner[@]}; do for j in seq 0 ${#i}; do echo -en "\b\b"; done; echo -ne "${i}"; sleep 0.2; done; done'

Display a list of RPMs installed on a particular date
Find out which RPMs were installed on a particular date. These would (naturally) include update RPMs. This example shows searching for "Thu 05 Mar" (with grep). Alternatively, pipe it to less so you can search inside less (with less's neat text highlighting of the search term): rpm -qa --queryformat '%{installtime} \"%{vendor}\" %{name}-%{version}-%{release} %{installtime:date}\n' | less # (this example) search term: Thu 05 Mar

Extract rpm package name, version and release using some fancy sed regex
This command could seem pretty pointless especially when you can get the same result more easily using the rpm builtin queryformat, like: $ rpm -qa --qf "%{NAME} %{VERSION} %{RELEASE}.%{ARCH}\n" | sort | column -t but nonetheless I've learned that sometimes it can be quite interesting trying to explore alternative ways to accomplish the same task (as Perl folks like to say: There's more than one way to do it!)

Mount a disk image (dmg) file in Mac OSX
To unmount, replace "attach" with "eject"

Countdown Clock
Simple countdown clock that should be quite portable across any Bourne-compatible shell. I used to teach for a living, and I would run this code when it was time for a break. Usually, I would set "MIN" to 15 for a 15-minute break. The computer would be connected to a projector, so this would be projected on screen, front and center, for all to see.

Remove all but one specific file

Multi-line grep
Using perl you can search for patterns spanning several lines, a thing that grep can't do. Append the list of files to above command or pipe a file through it, just as with regular grep. If you add the 's' modifier to the regex, the dot '.' also matches line endings, useful if you don't known how many lines you need are between parts of your pattern. Change '*' to '*?' to make it greedy, that is match only as few characters as possible. See also to do a similar thing with awk. Edit: The undef has to be put in a begin-block, or a match in the first line would not be found.

Extract audio stream from an video file using mencoder
This command extracts the audio stream of the video in $file and stores it in a file where the original suffix is changed to .mp3

Set audible alarm when an IP address comes online
Waiting for your server to finish rebooting? Issue the command above and you will hear a beep when it comes online. The -i 60 flag tells ping to wait for 60 seconds between ping, putting less strain on your system. Vary it to your need. The -a flag tells ping to include an audible bell in the output when a package is received (that is, when your server comes online).

Shortcut to find files with ease.
It looks for files that contains the given word as parameter. * case insensitive * matches files containing the given word.

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