in reply to Emulating command line pipe

my $pid = open IN, "tac yourlog.log | grep -m 1 /myapp/ |" or die $!;
while( <IN> ) {
    ## Do stuff
}
close IN;

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Re^2: Emulating command line pipe
by davistv (Acolyte) on Aug 31, 2007 at 16:51 UTC
    Thank you for your suggestion. This works fine in a script that gets executed at the command line, but when run as a cgi I see processes get split up, which prevents the -m 1 grep argument from killing tac:

    apache    2717  0.1  0.1   5112  3356 ?        S    12:42   0:00 /usr/
+bin/perl /w3/mysite.com/myapp/cgi-bin/myapp_sessions.cgi
apache    2920  0.0  0.0   2296  1024 ?        S    12:42   0:00 sh -c
+ tac /var/log/httpd/my_big_access_log | grep -m 1 /myapp/
apache    2921 24.9  0.0   1572   408 ?        R    12:42   0:07 tac /
+var/log/httpd/my_big_access_log

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    Here's my CGI version, would you have any other advice by chance?

    Thank You,
    Troy

    --- 
    #!/usr/bin/perl

use strict;
use CGI;
use Date::Parse;

my $log_dir = '/var/log/httpd/';
my $session_limit = 3600; # 1 hour

my ($sec,$min,$hour,$mday,$month,$year,$wday,$yday,$isdst) = localtime
+(time);
$year += 1900;
$month++;
my $date_cmp_str = join('', ($year, sprintf('%02d', $month), sprintf('
+%02d', $mday), $hour, $min, $sec));

my $cgiq = new CGI;
print $cgiq->header();
print '<html><head><title>myapp user status</title><link rel="styleshe
+et" href="/style/login.css" type="text/css" />';
print '<style type="text/css">li { font-size: 14px; }</style></head><b
+ody><h1>myapp user status</h1>';
print "\n<h2>Last known user activity:</h2>\n<ul>\n";
my @expired;
my @active;

opendir(DIR, $log_dir);
my @files = grep { /_access_log$/ } readdir(DIR);
closedir DIR;

print STDERR "Files = " . join(", ", @files) . "\n\n";

sleep(3);

foreach my $lf (@files) {
    # make sure this is an myapp site
    my ($domain, $t1, $t2) = split("_", $lf);
    my $myapp_dir = '/w3/' . $domain . '/myapp/';
    if (!-e $myapp_dir) {
        next;
    }
    else {
        # Find last login
        my $file = $log_dir . $lf;        
        my $last_line = '';
        my $pid = open IN, "tac $file | grep -m 1 /myapp/ |" or die $!
+;
        while( <IN> ) {
                $last_line = $_;
        }
        close IN;
        
        if ($last_line eq '') {
            # print "No login in logs.\n";
        }
        else {
            my ($ip, $d1, $d2, $date, $tz, $method, $url, $rest) = spl
+it(" ", $last_line);
            $date = substr($date, 1);
            $tz = substr($tz, 0, -1);
            my $cdate = $date . ' ' . $tz;
            my ($ss,$mm,$hh,$dy,$mon,$yr,$zone) = strptime($cdate);
            $yr += 1900;
            $mon++;
            my $date_str = join('', ($yr, sprintf('%02d', $mon), sprin
+tf('%02d', $dy), $hh, $mm, $ss));
            my ($domain, $t3, $t4) = split("_", $lf);
            
            if ($date_str > ($date_cmp_str - $session_limit)) {
                print "<li><font color='red'>User logged in! <a href='
+http://$domain'>$domain</a> last hit $mon/$dy/$yr $hh:$mm:$ss by IP $
+ip</font></li>\n";
            }
            else {
                print "<li>$domain last hit $mon/$dy/$yr $hh:$mm:$ss b
+y IP $ip</li>\n";
            }
        }
    }
}
print "</ul></body></html>";

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