System call problem

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

Replies are listed 'Best First'.
Re: System call problem by lhoward (Vicar) on Mar 08, 2001 at 20:28 UTC
Its generally considered good perl style to avoid doing system calls unnecessarily. In your case: instead of doung a system call to date, use localtime (or some other perl time function/module). Its generally less prone to unexpected errors and in many cases significantly faster to do it all in perl: `my ($day,$mon,$year)=(localtime(time))[3,4,5]; my $date=sprintf("%0d%02d%02d",$year+1900,$mon+1,$day);` [download] a quick benchmark on my system shows the localtime method is 39 times faster than the system call to date method: localtime: 4 wallclock secs ( 3.10 usr + 0.06 sys = 3.16 CPU) @ 30622.78/s (n=96768) sysdate: 31 wallclock secs ( 0.38 usr 3.65 sys + 11.15 cusr 2.36 csys = 17.54 CPU) @ 767.25/s (n=3092) using #!/usr/bin/perl -w use strict; use Benchmark; timethese(0, { sysdate => "chomp( my \$date = `date +\%Y\%m\%d` );", localtime => 'my ($day,$mon,$year)=(localtime(time) +)[3,4,5]; my $date=sprintf("%0d%02d%02d",$year+1900,$mon+1,$day);', }); [download]	[reply] [d/l] [select]
Re: Re: System call problem by Gloom (Monk) on Mar 08, 2001 at 20:40 UTC
exact ! I totaly agree with you, I avoid extra process creation when it's possible ( in complience with perlstyle I think :) _______________________ Hope this helps	[reply]
Re: System call problem by arturo (Vicar) on Mar 08, 2001 at 20:34 UTC
Better yet from a performance standpoint, spare yourself a `system` call and use the builtin `localtime`, à la: `sub get_date { my @time=(localtime)[3..5]; $time[2]+=1900; $time[1]++; foreach ($time[1], $time[0]) { $_ = '0'.$_ if $_ < 10; } "$time[2]$time[1]$time[0]"; }` [download] Yes, it's wordier, but adding this to your toolkit will allow you to cut n' paste it wherever you need it; you can also stick it in a module. Philosophy can be made out of anything. Or less -- Jerry A. Fodor	[reply] [d/l] [select]
Re: System call problem by arhuman (Vicar) on Mar 08, 2001 at 20:20 UTC
Err... the correct answer is RTFM but I'd rather tell you chomp (in case I would have missed something...) my $date = `date +%Y%m%d`; chomp $date; print "($date)"; [download] "Trying to be a SMART lamer" (thanx to Merlyn ;-)	[reply] [d/l]
Re: System call problem by Gloom (Monk) on Mar 08, 2001 at 20:23 UTC
Try chomp this remove the last character of a string, if it's a newline. this work also for an array ( processing each entry ). Becarefull, this function return true or false ( newline or not ) ! not the modified line. so my $date = chomp( `date ...` ); [download] will not return what you want, but chomp( my $date = `date ...` ); [download] does. ______________________ Hope this helps	[reply] [d/l] [select]
Re: System call problem by andye (Curate) on Mar 08, 2001 at 20:20 UTC
Tuna, have a look at perlfunc:chomp. andy.	[reply]
Re: System call problem by Jouke (Curate) on Mar 08, 2001 at 20:21 UTC
Use chop() to cut off the last character, or chomp() to remove the trailing 'record seperator' (which normally is the "\n", but could be something else on other platforms. hth, Jouke Visser, Perl 'Adept'	[reply]
Re: System call problem by Tuna (Friar) on Mar 08, 2001 at 20:29 UTC
Ok. I got it. Actually, although I forgot to post it originally, I did try: my $date = chomp( `date +%Y%m%d` ); [download] and thanks Gloom for correcting my syntax! And thx to all who replied!	[reply] [d/l]