Commands by realgt (1)

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Convert PNG to GIF
(relies on 'imagemagick') Convert all .png files to .gif. This can also go the other way if you reverse the file extensions in the command, e.g.: $ for file in *.gif; do convert "$file" "$(basename $file .gif).png"; done If the file is named 'example1.png' it will be named 'example1.gif' when it is complete.

Count the number of man pages per first character (a-z)
There once was a day I needed this info.

Returns the number of cores in a linux machine.
Original article in http://www.howtogeek.com/howto/ubuntu/display-number-of-processors-on-linux/

Grep log between range of minutes
Returns logs between HH:M[Mx-My], for example, between 13:40 and 13:45.

system beep off

Recursive Search and Replace
Finds the string in every file in an entire directory and all its subdirectories and replaces it with a new string. Especially useful when changing a machine's IP address or hostname - run it on /etc.

bulk rename files with sed, one-liner
Renames all files in a directory named foo to bar. foobar1 gets renamed to barbar1 barfoo2 gets renamed to barbar2 fooobarfoo gets renamed to barobarfoo NOTE: Will break for files with spaces AND new lines AND for an empty expansion of the glob '*'

Write comments to your history.
A null operation with the name 'comment', allowing comments to be written to HISTFILE. Prepending '#' to a command will *not* write the command to the history file, although it will be available for the current session, thus '#' is not useful for keeping track of comments past the current session.

Get all mac address
Get mac address listed for all interfaces.

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"


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