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renames multiple files that match the pattern
Useful when you want to quickly rename a bunch of files.

A DESTRUCTIVE command to render a drive unbootable
Overwrites the boot sector. Since this doesn't overwrite any data, you can usually recover by re-creating the partition table exactly the same as before you zeroed it. This can also help sometimes if you install a new drive in a Windows machine which can't read it.

View non-printing characters with cat
Useful to detect number of tabs in an empty line, DOS newline (carriage return + newline). A tool that can help you understand why your parsing is not working.

Swap a file or dir with quick resotre
This lets you replace a file or directory and quickly revert if something goes wrong. For example, the current version of a website's files are in public_html. Put a new version of the site in public_html~ and execute the command. The names are swapped. If anything goes wrong, execute it again (up arrow or !!).

Create user add lines from partial passwd file
Handy if you are installing a new server or recovering an old one and you have a passwd file with the accounts you want to add to the server. If you edit the file so that only the accounts that you want to add are left this line will spit out the correct useradd lines. The uid, gecos and shell will be preserved.

Remove empty directories
You can also use, $ find . -depth -type d -exec rmdir {} \; 2>/dev/null

Speak & Spell-esque glitch sounds
The Speak & Spell's sound chip uses a compressed audio format called "linear predictive coding". This command will read random bytes and attempt to decompress them as if it were audio data compressed in this format, then play it. This results in a unique sound which is similar to a glitching Speak & Spell.

Print a horizontal line
Replace the underscore with any other character. e.g. + or - or =

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"

Show a curses based menu selector
Not so much handy by itself, but very nice in shell scripts. This makes you a handy ncurses based checklist. Much like terminal installers, just use the arrow keys and hit 'Space' to adjust the selections. Returns all selected tags as strings, with no newline at the end. So, your output will be something like: "one" "two" "three" "four" "etc" For those who prefer bash expansion over gratuitious typing: $ whiptail --checklist "Simple checkbox menu" 12 35 3 $(echo {one,two,three,four}" '' 0"} ) Things to note: The height must includes the outer border and padding: add 7 to however many items you want to show up at the same time. If the status is 1, it will be selected by default. anything else, will be deselected.


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