Command line tips

The intention of this post is to collect a list of my favorite command line tips. Feel free to leave yours in the comment section.

• Instead of using clear you can just press ctrl-r.
• The command units can be used for any unit conversion you can imagine. See man page.
• You can use multitail to monitor multiple log files on a terminal.

Sources:

Give me that one command you wish you knew years ago

Mark Stosberg's bash tips
TechBar: Linux shell tips and tricks

Elapsed Time for Shell Scripts

A lot of times you want to calculate the time it takes for a part of a shell script to run. Here is one of the ways you can do this:

T1=$(date +%s)
# Do something here
T2=$(date +%s)
diffsec="$(expr $T2 - $T1)"
echo | awk -v D=$diffsec '{printf "Elapsed time: %02d:%02d:%02d\n",D/(60*60),D%(60*60)/60,D%60}'

This will tell you the elapsed time between setting T1 and setting T2. The output is formatted as HH:MM:SS and printed to the console. You can easily redirect to a file for logging.