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Manipulate the metadata when the photo was taken, this will shift with +15hours + 30min

Watch the progress of 'dd'
This version was mentioned in the comments. Credits go to flatcap.

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"

Delete all files by extension
This is a correction to https://www.commandlinefu.com/commands/view/22134 Use `-name` instead of `-iname`, because case-sensitivity is probably important when we're dealing with filenames. It's true that extensions are often capitalised (e.g., "something.JPG"), so choose whatever's appropriate. However, what is appropriate is the quoting of the name pattern, so the shell doesn't expand it incorrectly. Finally, `-delete` is clearer.

cat stdout of multiple commands

Convert CSV to JSON
Replace 'csv_file.csv' with your filename.

An alias to re-run last command with sudo. Similar to "sudo !!"
I didn't come up with this myself, but I always add this to my .bash_aliases file. It's essentially the same idea as running "sudo !!" except it's much easier to type. (You can't just alias "sudo !!", it doesn't really work for reasons I don't understand.) "fc" is a shell built-in for editing and re-running previous commands. The -l flag tells it to display the line rather than edit it, and the -n command tells it to omit the line number. -1 tells it to print the previous line. For more detail: $help fc

processes per user counter
use Linux ;)

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 http://www.commandlinefu.com/commands/view/1764/display-a-block-of-text-with-awk 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.

Relocate a file or directory, but keep it accessible on the old location throug a simlink.
Used for moving stuff around on a fileserver


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