I am trying to do following:
Get output of free -mo , take the 2nd line and log it to a file every 30 seconds.
When I run
$free -mo -s 30
It runs and displays output every 30 seconds.
But when I run
$ free -mo -s 30 | head -2 | tail -1
It runs only once. I am not able to figure out what is wrong.
free Manual says free -s 30 run the command every 30 seconds.
head -2 returns only the first 2 lines of output then quits. tail -1 returns the last line, then quits. When any program quits in a pipeline, it kills the entire pipeline, so free is stopped when head and tail finish.