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Use socat to emulate an SMTP mail SERVER
Lots of scripts show you how to use socat to send an email to an SMTP server; this command actually emulates an SMTP server! It assumes the client is only sending to one recipient, and it's not at all smart, but it'll capture the email into a log file and the client will stop retrying. I used this to diagnose what emails were being sent by cron and subsequently discarded, but you can use it for all sorts of things.

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

Know which version dpkg/apt considers more recent
Compares two versions with dpkg. It is not always obvious what version dpkg/apt will consider to be more recent. Operators include the following : * These treat an empty version as earlier than any version: lt le eq ne ge gt. * These treat an empty version as later than any version: lt-nl le-nl ge-nl gt-nl. * These are provided only for compatibility with control file syntax: < > >. This command doesn't output anything. It only returns with status 0 or 1, hence the echo "y" || echo "n" to get an output.

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

"Pretty print" $PATH, separate path per line
from: http://www.unix.com/shell-programming-and-scripting/28047-split-print-path.html

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

find read write traffic on disk since startup
The iostat command is used for monitoring system input/output device loading by observing the time the devices are active in relation to their average transfer rates. in ubuntu to get the iostat program do this: sudo apt-get install sysstat i found this command here: http://www.ocztechnologyforum.com/forum/showthread.php?t=54379

Finding the number of cpu's

which process is accessing the CDROM

Enable cd by variable names
Usage: $ mydir=/very/long/path/to/a/dir $ cd mydir I often need to cd where no man wants to go (i.e. long path). by enabling the shell option cdable_vars, I can tell cd to assume the destination is the name of a variable.


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