Nicolás Brailovsky

Unix trivia day: in the olden days of the 90’s there were a lot of Unix boxes out there named “elvis”. Nowdays it’s not uncommon to find one, either. Have you ever wondered why are there so many boxes called elvis?

This is related to Solaris’ ping command. When you ping $HOST it prints “$HOST is alive” (if it’s responding the pings), thus elvis is alive!

The other day I had to create one of those “enum to string” functions. They really suck, always getting out of sync, so I made a script to auto-update the header file containing this function… just add a target to the makefile and you’re done!

Anyway, this is the part of the script I came up with to get the enum elements:

cat enum_definition.h | sed -n ‘/enum OID/,/\}\;/ s/\(.*\)/\1/p’

Nice voodoo, isn’t it? How the hell are you supposed to understand that? Well, you’re not, sed is write-only-code, but you can try reading http://www.grymoire.com/Unix/Sed.html#toc-uh-25, a great sed introduction.

Have fun!

You can easily schedule a command using “at”, which recognizes a nicely formatted date string. For example: $ at today 3:00 AM This will open a prompt. So, for example: $ at today 3:30 PM > wget foobar.com/a_huge_file > C-D Will schedule a download of a huge file, today at 3:00 AM. Nice, isn’t it? To check the whole list of accepted formats check the man for at.

One last note: at will “remember” the current environment variables, so PWD, USER, OLD_DIR and all that will be the same. This means if you schedule a command with a relative path it’ll still work!