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vmstat/iostat with timestamp
Also useful with iostat, or pretty much anything else you want timestamped.

Email someone if a web page has been updated.
A cronjob command line to email someone when a webpages homepage is updated.

Remove duplicate rows of an un-sorted file based on a single column
The command (above) will remove any duplicate rows based on the FIRST column of data in an un-sorted file. The '$1' represents a positional parameter. You can change both instances of '$1' in the command to remove duplicates based on a different column, for instance, the third: $ awk '{ if ($3 in stored_lines) x=1; else print; stored_lines[$3]=1 }' infile.txt > outfile.txt Or you can change it to '$0' to base the removal on the whole row: $ awk '{ if ($0 in stored_lines) x=1; else print; stored_lines[$0]=1 }' infile.txt > outfile.txt ** Note: I wouldn't use this on a MASSIVE file, unless you're RAM-rich ;) **

Create a new file

Selecting a random file/folder of a folder
Also looks in subfolders

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"

Generate a ZenCart-style MD5 password hash.
ZenCart uses a MD5 with a salt to secure its passwords. If you need to forcibly change someone's password to a known value within the database, this one-liner can generate the password. Change the value of 'p' to the password you want.

Download all mp3's listed in an html page

Short and sweet output from dig(1)
Turn off almost all of dig's output except for what you'd see in a zone file. This can also be put into ~/.digrc.

Export OPML from Google Reader


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