Many shell programmers are in the habit of using calls to external commands

instead of using shell built-in commands (an example of this is a call to

usr/bin/echo instead of using the echo command built into the shell.

This script shows sh_wasted.d tracing a shell script that calls /usr/bin/echo

instead of using the built-in.

# sh_wasted.d -c ./func_waste.sh

Tracing... Hit Ctrl-C to end.

Function A

Function B

Function C

Script duration: 3101631 us

External command elapsed times,

FILE NAME TIME(us)

func_waste.sh sleep 3019573

Wasted command elapsed times,

FILE NAME TIME(us)

func_waste.sh /usr/bin/echo 26510

You can see that the calls to /usr/bin/echo took around 26 thousand

microseconds; time wasted by the shell having to access an external command.

Here we trace the same script, except it uses the shell built-in echo command.

# sh_wasted.d -c ./func_abc.sh

Function A

Tracing... Hit Ctrl-C to end.

Function B

Function C

Script duration: 3032616 us

External command elapsed times,

FILE NAME TIME(us)

func_abc.sh sleep 3012920

Wasted command elapsed times,

FILE NAME TIME(us)

The total time here is less and there are no 'wasted' calls to external

commands.