linux – 为什么即使文件被锁定,File :: FcntlLock的l_type总是

为什么它返回0并且打印/tmp/test.pid被解锁.即使文件被锁定了？

sub getPidOwningLock {
    my $filename = shift;

    my $fs = new File::FcntlLock;
    $fs->l_type( F_WRLCK );
    $fs->l_whence( SEEK_SET );
    $fs->l_start( 0 );
    $fs->l_len( 0 );

    my $fd;
    if (!open($fd,'+<',$filename)) {
        print "Could not open $filenamen";
        return -1;
    }

    if (!$fs->lock($fd,F_GETLK)) {
        print "Could not get lock information on $filename,error: $fs->errorn";
        close($fd);
        return -1;
    }

    close($fd);

    if ($fs->l_type() == F_UNLCK) {
        print "$filename is unlocked.n";
        return 0;
    }

    return $fs->l_pid();
}

该文件被锁定如下(lock.sh)：

#!/bin/sh
(
    flock -n 200
    while true; do sleep 1; done
) 200>/tmp/test.pid

该文件确实已锁定：

~$./lock.sh &
[2] 16803
~$lsof /tmp/test.pid
COMMAND   PID  USER   FD   TYPE DEVICE SIZE/OFF   NODE NAME
bash    26002 admin  200w   REG    8,5        0 584649 test.pid
sleep   26432 admin  200w   REG    8,5        0 584649 test.pid