timing a command execution with perl

savio has asked for the wisdom of the Perl Monks concerning the following question:

Replies are listed 'Best First'.
Re: timing a command execution with perl by LanX (Saint) on Dec 09, 2014 at 14:33 UTC
You can use `Time::HiRes` to get `time` within Perl execution. But please keep in mind that the OS produces loads and overheads due to multitasking which will add to execution time. Cheers Rolf _{(addicted to the Perl Programming Language and ☆☆☆☆ :)}	[reply]
Re: timing a command execution with perl by fishmonger (Chaplain) on Dec 09, 2014 at 14:27 UTC
Why would you want to install/use Time::HR? That module hasn't been maintained since 2002. Instead, you should look at using Time::HiRes, which is a core module.	[reply]
Re^2: timing a command execution with perl by Anonymous Monk on Dec 09, 2014 at 14:51 UTC
Ok, I installed the Time::HiRes module but how can I use it, it seems ot me a bit complicated. In addition, I'm working at a real-time work. I have to be as much precise as I can.	[reply]
Re^3: timing a command execution with perl by fishmonger (Chaplain) on Dec 09, 2014 at 15:09 UTC
If you post a short but complete test script and point out what you want to time, we will be better able to assist you in using the module to time that portion.	[reply]
Re: timing a command execution with perl by james28909 (Deacon) on Dec 09, 2014 at 15:03 UTC
Here is an example: `use strict; use warnings; use diagnostics; use Time::HiRes qw( time ); my $start = time(); ...code goes here... my $end = time(); my $runtime = sprintf("%.16s", $end - $start); print "This script took $runtime seconds to execute\n";` [download]	[reply] [d/l]
Re^2: timing a command execution with perl by johngg (Canon) on Dec 09, 2014 at 15:40 UTC
Using `gettimeofday` and `tv_interval` makes it a bit simpler. `$ perl -Mstrict -Mwarnings -MTime::HiRes=gettimeofday,tv_interval -E ' my $t0 = [ gettimeofday() ]; my @psLines = qx{ ps -ef }; print qq{Command took }, tv_interval( $t0, [ gettimeofday() ] ), qq{ seconds to run\n};' Command took 0.015902 seconds to run $` [download] I hope this is helpful. Cheers, JohnGG	[reply] [d/l] [select]
Re^2: timing a command execution with perl by Anonymous Monk on Dec 09, 2014 at 15:38 UTC
so I should write: `use strict; use warnings; use diagnostics; use Time::HiRes qw( time ); my $start = time(); system("program-name file-name"); my $end = time(); my $runtime = sprintf("%.16s", $end - $start); print "This script took $runtime seconds to execute\n";` [download] isn't it?	[reply] [d/l]
Re^3: timing a command execution with perl by james28909 (Deacon) on Dec 09, 2014 at 15:53 UTC
I mean something like: use strict; use warnings; use diagnostics; use Time::HiRes qw( time ); my $start = time(); stringsNthings(); your actual code goes here; whether it be system(whatever_prog, whatever_arg); or sub stringsNthings{ my $hello_world = "hello world\n"; my $sum = 1 + 2; chomp(my name = <STDIN>); } print stringsNthings($hello_world); print stringsNthings($sum."\n"); print stringsNthings($name); my $end = time(); my $runtime = sprintf("%.16s", $end - $start); print "This script took $runtime seconds to execute\n"; [download] As long as you put working code in there it should time it. The code posted more than likely wont work, its just a visual example.	[reply] [d/l]
Re^3: timing a command execution with perl by Anonymous Monk on Dec 09, 2014 at 15:44 UTC
That measures the elapsed real time (wall clock time), not CPU time. Which do you want to measure?	[reply]
Re^2: timing a command execution with perl by Anonymous Monk on Dec 09, 2014 at 15:45 UTC
Is there some options to visualise also microseconds and milliseconds and not only seconds?	[reply]
Re^3: timing a command execution with perl by james28909 (Deacon) on Dec 09, 2014 at 16:06 UTC
Yes, Time::HiRes like posted here: http://www.perlmonks.org/?node_id=1109765	[reply]
Re: timing a command execution with perl by Anonymous Monk on Dec 09, 2014 at 14:53 UTC
Why not use the program time?	[reply]
Re^2: timing a command execution with perl by Anonymous Monk on Dec 09, 2014 at 14:59 UTC
Indeed I used it in my perl program: `system("time", "program-name", "file-name");` but the out is different (and confused) with respect to that right output I have just typing `time program-name file-name` in the shell.	[reply] [d/l] [select]
Re^3: timing a command execution with perl by Anonymous Monk on Dec 09, 2014 at 15:07 UTC
time typically outputs its values to `STDERR` (unless your version supports the `-o` option). To capture `STDERR` in a Perl program, something like Capture::Tiny or IPC::Run3 makes that easy. (Or you can use shell redirects.)	[reply] [d/l] [select]