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create a nicely formatted example of a shell command and its output
Shell function which takes a bash command as its input, and displays the following formatted output: EXAMPLE: command OUTPUT: output from command

Prevent non-root users from logging in
Also with optional message: $ echo "no login for you" > /etc/nologin (This doesn't affect your current X session - you're already logged in!)

Make a statistic about the lines of code
use find to grep all .c files from the target directory, cat them into one stream, then piped to wc to count the lines

Follow the most recently updated log files
This command finds the 5 (-n5) most frequently updated logs in /var/log, and then does a multifile tail follow of those log files. Alternately, you can do this to follow a specific list of log files: sudo tail -n0 -f /var/log/{messages,secure,cron,cups/error_log}

Mount important virtual system directories under chroot'ed directory
The command is useful when, e.g., booting an existing system with a rescue or installation CD where you need to chroot into the hard-disk and be able to do stuff which accesses kernel info (e.g. when installing Ubuntu desktop with LVM2 you need to mount and chroot the hard disk from a shell window in order to install packages and run initramfs inside chroot). The command assumes that /mnt/xxx is where the chroot'ed environment's root file system on the hard disk is mounted.

Change size of lots of image files.
Imagemagick library is used.

Check if your desired password is already available in haveibeenpwnd database. This command uses the API provided by HIBP

most used unix commands

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

Get the next weekday for an 'at' command
Line can be modified as needed. This considers weekdays to be Mon-Fri. If run any working day it'll provide a parameters for the next working day for "at". "beep" provided as a sample command. This can be modified easily to include wait time. If you need something to run "D" days after today: # D=4;if [ $(date +%u --date="${D} days") -lt 5 ];then AT="+${D} days";else AT="next monday";fi; echo "beep" | at noon ${AT}


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