Command-line Kung Fu

I recently stumbled on an article on Lifehacker that suggested a way to learn Linux commands in-line with your daily systems administration.  Basically, it calls for adding a string of commands to your .bashrc file that randomly selects a command from various bin directories and executes a whatis on them.

I thought it was brilliant, but when I went to try it I was bummed to find out that the shuf command is not shipped with the base distribution of CentOS, which is the primary OS I support.  Because of this, I decided to spin my own version of the hack that will work on CentOS.

# RANDOM COMMAND-LINE KNOWLEDGE

# List of bin directories that include commands you'd like to learn
binDirs='/bin /usr/bin /usr/sbin /sbin'

# Count the number of commands in $binDirs and randomly select a number in the range
randomNum=$(expr $RANDOM % $(ls $binDirs | wc -l))

# Based on the selected $randNum, select the corresponding command
randomCmd=$(ls $binDirs | head -${randomNum} | tail -1)

# Lookup the command with whatis and display the results
echo "Did you know that:"
whatis $randomCmd | sed 's/^/\t/g'

The hack isn't perfect because not all commands have an entry in the whatis database.  When this happens, you will see a response similar to this:

Did you know that:

        numastat: nothing appropriate

But, this doesn't happen all that often, and with this hack, I've discovered some awesome commands like watch.

Did you know that:
        watch                (1)  - execute a program periodically, showing output fullscreen