G'day DRVTiny,

Welcome to the Monastery.

"When i using perl -c it takes too much time to check ..."

As I came to post this, I saw that ++vr had posted a Win32 solution. Our code is functionally similar up to the point of getting the perl -c exit code; then our methods diverge somewhat. Our general thinking about the problem was also very similar: don't let perl -c run for as long as it likes; let it run for as long as you like.

Here's my code.

#!/usr/bin/env perl

use strict;
use warnings;
use constant {
    TIMEOUT_USECS => 100000,
    MIN_LINES_TO_ASSESS => 10,
    OUT_FILE => 'pm_11114214_minimal_is_perl_test.out',
};
use constant CMD_LINE => 'perl -c IN_FILE 2> ' . OUT_FILE;

use Time::HiRes 'ualarm';

for my $file (@ARGV) {
    my $cmd = CMD_LINE;
    $cmd =~ s/IN_FILE/$file/;

    eval {
        local $SIG{ALRM} = sub { die };
        ualarm TIMEOUT_USECS;
        `$cmd`;
        $? and die;
        ualarm 0;
        print "$file is valid Perl code.\n";
        1;
    }
    or do {
        ualarm 0;
        heuristic_check($file);
    };
}

sub heuristic_check {
    my ($file) = @_;

    if (-z OUT_FILE) {
        print "$file could be Perl code.\n";
    }
    else {
        my $file_lines = (split ' ', `wc -l $file`)[0];
        my $out_lines = (split ' ', `wc -l @{[OUT_FILE]}`)[0];

        if ($file_lines < MIN_LINES_TO_ASSESS) {
            print "$file is too small to assess. [$file_lines lines]\n
+";
        }
        elsif ($out_lines > $file_lines) {
            print "$file does not look like Perl code.\n";
        }
        else {
            printf "%s has a %.02f%% chance of being Perl code\n",
                $file, 100 * ($file_lines - $out_lines) / $file_lines;
        }
    }

    return;
}
[download]

With the timeout set to 1ms, it assessed itself as "a 98.18% chance of being Perl code"; at 10ms it was a tad more confident with "a 98.25% chance of being Perl code"; and at 100ms, it was sure, with "is valid Perl code".

I tested a tiny text file I had in my tmp directory. It wasn't Perl and I decided tiny files were too small to assess if they didn't pass perl -c. In that case, the output showed "too small to assess. [6 lines]". However, I did create a file with just print "Hello, world!\n";. That gave "hello.pl is valid Perl code." at 100ms but, at 10ms, the output was "hello.pl is too small to assess. [1 lines]".

And I tested a plain text file containing no Perl code: that gave "does not look like Perl code" at 1ms, 10ms and 100ms.

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