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Is today the last day of the month?
Nice simple example of something we can do in bash.

Sum columns from CSV column $COL
More of the same but with more elaborate perl-fu :-)

Listing today’s files only

Clear cassandra snapshots that are older than 30 days
Better than: $ nodetool clearsnapshot

Count opening and closing braces in a string.
This function counts the opening and closing braces in a string. This is useful if you have eg long boolean expressions with many braces and you simply want to check if you didn't forget to close one.

Is it a terminal?
Oddly, the isatty(3) glibc C call doesn't have a direct analogue as a command 'isatty(1)'. All is not lost as you can use test(1). For example, your script might be run from a tty or from a GUI menu item but it needs to get user-input or give feedback. Now your script can test STDIN with 'isatty 0' or STDOUT with 'isatty 1' and use xmessage(1) if the tty is not available. The other way to test for this is with 'tty -s' - but that's only for STDIN.

How to search for files and open all of them in tabbed vim editor.
Opening several files at once in Vim can be very easy in connection with find command.

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"

Find Malware in the current and sub directories by MD5 hashes
Command makes use of the Malware Hash Registry (http://www.team-cymru.org/Services/MHR/). It parses the current directory and subdirectories and calculates the md5 hash of the files, then prints the name and sends the hash to the MHR for a lookup in their database. The 3rd value in the result is the detection percentage across a mix of AV packages.

list block devices
Shows all block devices in a tree with descruptions of what they are.


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