#!/usr/bin/perl

use Getopt::Std;
my $opts = 'ulhIive:F:q';
getopts($opts) or usage();
my $pat = defined($opt_e) ? $opt_e : @ARGV ? shift : usage();
my $qr = $opt_i ? qr/$pat/i : qr/$pat/;

my $format;

if (defined $opt_F) {
  $format = $opt_F . "\n";
} else {
  my %format = (l => '%s'."\n",
                h => '%2$s'."\n",
                q => "",
                "" => $opt_I || @ARGV > 1 ? "%s: %s\n" : '%2$s'."\n",
               );
  my $fk = "";
  $fk .= 'l' if $opt_l;
  $fk .= 'h' if $opt_h;
  $fk .= 'q' if $opt_q;
  $format = $format{$fk};
  unless (defined $format) {
    warn "Incompatible options.\n";
    usage();
  }
}

$| = 1 if $opt_u;

$rc = 1;  # No matches;

if ($opt_I) {
  while (<STDIN>) { chomp; do_file($_) }
} elsif (@ARGV) {
  do_file($_) for @ARGV;
} else {
  do_file(\*STDIN);
}
exit $rc;

sub do_file {
  my $file = shift;
  my $fh;
  if (ref $file) {
    $fh = $file;
    $file = "<stdin>";
  } else {
    return if -d $file;
    unless (open $fh, "<", $file) {
      warn "Couldn't open '$file': $!; skipping\n";
      return;
    }
  }

  while (<$fh>) {
    chomp;
    if (/$qr/ ^ $opt_v) {
      $rc = 0;                  # match
      printf $format, $file, $_, $.;
      return if $opt_l;
    }
  }
}

sub usage {
  print STDERR <<EOM;
 Usage: $0 [$opts] pattern files...

    -F format    printf-style output format 
                 (%1\$s = filename, %2\$s = text, %3\$d = line number)
    -e pattern   specify pattern
    -h           omit filenames
    -i           case-insensitive match
    -I           list of files on STDIN instead of in ARGV
    -l           print filenames only
    -q           print nothing
    -u           make output unbuffered
    -v           invert matching
EOM
  exit 2;
}