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.