perl 对文件句柄加锁

perl  2.pl

#!/usr/bin/perl -w
use strict;
use Fcntl qw(:DEFAULT :flock);
open B,">>a.txt";
foreach(1..50)
{
        flock(B,LOCK_EX);

#select B;
#select STDOUT;

        print B "1";
        print B "A\n";
        $|=1;

#syswrite STDOUT, "A";
        flock(B,LOCK_UN);
        sleep 10;
}

close B;

perl 3.pl

#!/usr/bin/perl -w
use strict;
use Fcntl qw(:DEFAULT :flock);
open F,">>a.txt";
foreach(1..50)
{
        flock(F,LOCK_EX);
#select F;
#select STDOUT;
#while(<F>)
#       {
#               print ". $_\n";
#       }

        print F "2";
        print F "B\n";
        $|=1;

        flock(F,LOCK_UN);
        sleep 1;
#syswrite STDOUT ,"NEXT\n";
}

close F;