perl 输出过滤

[perl]代码库

#-----------------------------
head ( 100 );
while ( <> )
{
	print;
}

sub head
{
	my $lines = shift || 20;
	return if $pid = open ( STDOUT, "|-" );
	die "cannot fork: $!" unless defined $pid;
	while ( <STDIN> )
	{
		print;
		last unless --$lines ;
	}
	exit;
}
#-----------------------------
1:
> Welcome to Linux, version 2.0.33 on a i686

2:
>

3:
>     "The software required `Windows 95 or better',

4: >      so I installed Linux."
#-----------------------------
> 1:
Welcome to Linux, Kernel version 2.0.33 on a i686

> 2:

> 3:     "The software required `Windows 95 or better',

> 4:      so I installed Linux."
#-----------------------------
# download the following standalone program
#!/usr/bin/perl
# qnumcat - demo additive output filters

number();
# push number filter on STDOUT
quote();
# push quote filter on STDOUT

while ( <> )
{
# act like /bin/cat
	print;
}

close STDOUT;
# tell kids we're done--politely
exit;

sub number {
    my $pid;
    return if $pid = open(STDOUT, "|-");
    die "cannot fork: $!" unless defined $pid;
while (<STDIN>) { printf "%d: %s", $., $_ }
exit;
}

sub quote {
    my $pid;
    return if $pid = open(STDOUT, "|-");
    die "cannot fork: $!" unless defined $pid;
while (<STDIN>) { print "> $_" }
exit;
}

#-----------------------------