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Get line count for any file ending with extension recursively rooted at the current directory.

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"

Backup with versioning
Apart from an exact copy of your recent contents, also keep all earlier versions of files and folders that were modified or deleted. Inspired by EVACopy http://evacopy.sourceforge.net

Switch to a user with "nologin" shell
You need sudo privileges for this command. Replace username with actual username.

for ssh uptime
This will run them at the same time and timeout for each host in ten seconds. Also, mussh will append the ip addres to the beginning of the output so you know which host resonded with which time. The use of the sequence expression {1..50} is not specific to mussh. The `seq ...` works, but is less efficient.

Convert unix timestamp to date
The "-d" option for gnu's "date" command can calculate positive or negative offset from any time, including "now". You can even specify a source timezone (the output timezone can be set with the TZ environment variable). Useful! Fun! Not very well documented!

formatting number with comma
it is not work with Cygwin's bash3.X. Test in Linux. use printf "%'f" number while it is floating point number

Detect illegal access to kernel space, potentially useful for Meltdown detection
Based on capsule8 agent examples, not rigorously tested

Insert a line at the top of a text file without sed or awk or bash loops
Yet another way to add a line at the top a of text file with the help of the tac command (reverse cat).

Recursive search and replace (with bash only)
Replaces a string matching a pattern in one or several files found recursively in a particular folder.


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