Commands using cat (514)

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do something else while waiting for an event, such as reboot
until (ssh root@10.1.1.39 2> /dev/null); do date; sleep 15; done In this case will execute "date" then "sleep 15" until we are able to ssh into server, such as after a reboot Could also be like: until ( ping 10.1.1.39 1> /dev/null); do echo "server 10.1.1.39 is down"; sleep 15; done

Binary digits Matrix effect
Prints 0's and 1's in The Matrix style. You can easily modify to print 0-9 digits using $RANDOM %10 insted of %2.

rgrep: recursive grep without .svn
Only excludes .svn from filenames.

List all installed PERL modules by CPAN
This command will give you the detailed information about the installed perl modules i.e. installed path, Link type, version, files etc.

updatedb for MAC OSX
MAC OSX doesn't come with an updatedb command by default, this will emulate the updatedb thats on a typical Linux OS. Simply add it to your ~/.bash_profile

Parse YouTube url (get youtube video id)
url can be like any one of followings: $url="MejbOFk7H6c" $url="http://youtu.be/MejbOFk7H6c" $url="https://youtube.com/watch?feature=player_embedded&v=MejbOFk7H6c#t" $url="//www.youtube.com/v/MejbOFk7H6c?hl=ru_RU&version=3&rel=0" $url="http://www.youtube.com/embed/MejbOFk7H6c?feature=player_embedded" If url mismatching, whole url will be returned.

Display a random man page
I'm not sure why you would want to do this, but this seems a lot simpler (easier to understand) than the version someone submitted using awk.

delete a line from your shell history
If you're a moron like me, sometimes your fingers get away from you and you, for example, enter your password when you're already authenticated to ssh-agent, sudo, etc., and your password ends up in shell history. Here's how to get it out.

Delete all non-printing characters from a file
tr has some predefined sets of characters that are more convenient to use than characters codes

Short and elegant way to backup a single file before you change it.
Remember to backup everything before changing it so you can restore all to normal.


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