Hi guys,

I am working on a logging module. I was just studying the existing perl log modules and read that - syswrite is useful in a condition like logging as during its write operation it prevents someone else from writing at the same time. To verify that I wrote a small perl program

#!/usr/bin/perl -w
use strict;
use Fcntl;
$| = 1;

sub testme {
    my ($flag, $data) = @_;
    if ($flag == 1) {
        sysopen(FILE, 'bangbang',  O_WRONLY | O_APPEND |  O_CREAT);
        while (1) {
            syswrite FILE, "$data\n";
        }
    } else {
        open(FILE, ">>bangbang");
        while (1) {
            print FILE "$data\n";
        }
    }
    close(FILE);
}

testme($ARGV[0], $ARGV[1]);
[download]

Testing both for syswrite and print - I found that $data printing in file is corrupted when I run 2 instances of the same program together. But using syswrite saves me from that. It has every line intact and no line is a mix of different data sets of the 2 programs.

But what struck me more was the size of the files created when I ran the following programs together:

1. ./program 1 first
2. ./program 1 second

this uses syswrite to write and check whether 'first' and 'second' clobber each other. During this run, I got the following stats:

1st run - 30 seconds - file size 40 MB
2nd run - 50 seconds - file size 61 MB

Now for the print run,

1. ./program 2 first
2. ./program 2 second

this uses print to write and check whether 'first' and 'second' clobber each other. During this run, I got the following stats:

1st run - 30 seconds - file size 315 MB
2nd run - 50 seconds - file size 586 MB

I was running a VM so I know that my profiling wouldn't be so accurate. But still, I had done autoflush for both syswrite and print. And I read somewhere that for output greater than 3 KB syswrite is faster?

Is print faster than syswrite? Is my testing flawed? Am I missing something? What would you use if you had to write a logging module in perl - print or syswrite? and why?

Thanks for going through my post.

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