Timing techniques solution

(happy music)…- [Instructor] Let's look at the solutions…to the little challenge problem.…I typed in the loop1.sh script.…Notice, I'm using the pwd command,…and we're going to go 50,000 times here.…We want to time it, so we'll just say time ./loop1.sh,…and that took, on this computer, 6/10ths of a second.…

Pretty darn quick.…Let's just check, type pwd, and it's a shell built in.…A shell built in means the shell itself, bash itself,…when it sees pwd, it's just going to do it,…doesn't have to go search for a command with that name…and launch a new process for it, it just does it.…Now, let's edit loop1.sh,…and change the pwd to actually run the command in pwd.…

Just to check, there it is, executable program, so forth.…Let's time it now.…My goodness, took 21.5 seconds, and a lot more CPU time.…Big difference, isn't it?…We had time to get a good drink of coffee there.…Let's now investigate what's going on.…Right now, this script uses bin/pwd,…let's do an strace, counting information,…send the output to /tmp/s.out, and we run the script.…