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      1 Many shell programmers are in the habit of using calls to external commands 
      2 instead of using shell built-in commands (an example of this is a call to
      3 usr/bin/echo instead of using the echo command built into the shell.
      4 
      5 This script shows sh_wasted.d tracing a shell script that calls /usr/bin/echo
      6 instead of using the built-in.
      7 
      8 # sh_wasted.d -c ./func_waste.sh
      9 Tracing... Hit Ctrl-C to end.
     10 Function A
     11 Function B
     12 Function C
     13 Script duration: 3101631 us
     14 
     15 External command elapsed times,
     16    FILE                           NAME                   TIME(us)
     17    func_waste.sh                  sleep                   3019573
     18 
     19 Wasted command elapsed times,
     20    FILE                           NAME                   TIME(us)
     21    func_waste.sh                  /usr/bin/echo             26510
     22 
     23 You can see that the calls to /usr/bin/echo took around 26 thousand
     24 microseconds; time wasted by the shell having to access an external command.
     25 
     26 
     27 Here we trace the same script, except it uses the shell built-in echo command.
     28 
     29 # sh_wasted.d -c ./func_abc.sh 
     30 Function A
     31 Tracing... Hit Ctrl-C to end.
     32 Function B
     33 Function C
     34 Script duration: 3032616 us
     35 
     36 External command elapsed times,
     37    FILE                           NAME                   TIME(us)
     38    func_abc.sh                    sleep                   3012920
     39 
     40 Wasted command elapsed times,
     41    FILE                           NAME                   TIME(us)
     42 
     43 The total time here is less and there are no 'wasted' calls to external
     44 commands.
     45 
     46