#!/usr/bin/perl -w
#  hh, jan 2001: filter stdin lines for presence or absence of phrases

my @must = () ;
my @dont = () ;
my @ormust = () ;

my $usage = qq{
usage:
filter.pl {+|-|:|++|--|::exp} [file]\t\t(c) 2001 hellweg\@snark.de
+/-/: filter verbatim, ++/--/:: filter regexp
+ :must occur
- :must not occur
: :at least one of the ':'ed exp must occur
output lines that contain all of the +patterns, none of the -patterns
and/or at least one of the ':' patterns... often easier than grepping

License to use, modify and redistribute granted to each and every lifeform on
this planet (as long as credit to hellweg\@snark.de remains). No guarantee that
'filter' does or does not perform the way you want...
} ;

my ($par, $fil ) = ();
$par = shift || die $usage ;

while(defined($par)) {
    if($par =~ /^--(.+)/) {
	push @dont, $1 ;
    }
    elsif($par =~ /^-(.+)/) {
	push @dont, quotemeta($1) ;
    }
    elsif($par =~ /^\+\+(.+)/) {
	push @must, $1 ;
    }
    elsif($par =~ /^\+(.+)/) {
	push @must, quotemeta($1) ;
    }
    elsif($par =~ /^\:\:(.+)/) {
	push @ormust, $1 ;
    }
    elsif($par =~ /^\:(.+)/) {
	push @ormust, quotemeta($1) ;
    }
    else {
	$file = $par ;
    }
    $par = shift ;
}

my $ormust = 0 ;
$ormust = "(" . join(")|(", @ormust). ")"  if(scalar(@ormust)) ;

if(defined($file)) {
    close(STDIN) ;
    open(STDIN, "<$file") || die "can not read $file\n" ;
}

LOOP:
while(<STDIN>) {
    next LOOP if($ormust && (! /$ormust/)) ;
    foreach $pat (@must) {
	next LOOP if(! /$pat/) ;
    }
    foreach $pat (@dont) {
	next LOOP if( /$pat/) ;
    }
    print ;
}