Performance profiling tools for shell scripts

You can set PS4 to show the time and line number. Doing this doesn't require installing any utilities and works without redirecting stderr to stdout.

For this script:

#!/bin/bash -x# Note the -x flag above, it is required for this to workPS4='+ $(date "+%s.%N ($LINENO) ")'for i in {0..2}do    echo $idonesleep 1echo done

The output looks like:

+ PS4='+ $(date "+%s.%N ($LINENO) ")'+ 1291311776.108610290 (3) for i in '{0..2}'+ 1291311776.120680354 (5) echo 00+ 1291311776.133917546 (3) for i in '{0..2}'+ 1291311776.146386339 (5) echo 11+ 1291311776.158646585 (3) for i in '{0..2}'+ 1291311776.171003138 (5) echo 22+ 1291311776.183450114 (7) sleep 1+ 1291311777.203053652 (8) echo donedone

This assumes GNU date, but you can change the output specification to anything you like or whatever matches the version of date that you use.

Note: If you have an existing script that you want to do this with without modifying it, you can do this:

PS4='+ $(date "+%s.%N ($LINENO) ")' bash -x scriptname

In the upcoming Bash 5, you will be able to save forking date (but you get microseconds instead of nanoseconds):

PS4='+ $EPOCHREALTIME ($LINENO) '

You could pipe the output of running under -x through to something that timestamps each line when it is received. For example, tai64n from djb's daemontools.At a basic example,

sh -x slow.sh 2>&1 | tai64n | tai64nlocal

This conflates stdout and stderr but it does give everything a timestamp.You'd have to then analyze the output to find expensive lines and correlate that back to your source.

You might also conceivably find using strace helpful. For example,

strace -f -ttt -T -o /tmp/analysis.txt slow.sh

This will produce a very detailed report, with lots of timing information in /tmp/analysis.txt, but at a per-system call level, which might be too detailed.

Sounds like you want to time each echo. If echo is all that you're doing this is easy

alias echo='time echo'

If you're running other command this obviously won't be sufficient.