如何在perl中grep读取文件

Question

I would like to read a file in perl, after, the user can input any string and grep will try to find the string inputted in the file read. It will only exit when the user input nothing or any space character. Here's my code which is not working:

#! usr/bin/perl
use warnings;
use strict;

open MATCHSTRING,"matchstring";
my @lines = <MATCHSTRING>;

while (<>) {
    chomp;
    my @match = grep {/\b$_\b/s} @lines;
    print @match;
    }

I'm still lacking the condition where it will exit once nothing is inputted or a newline or any space character.

Answer 1

while (<>)

means

while (defined($_ = <>))

so need to press Ctrl-D (unix) or Ctrl-Z, Enter (Windows) to signal end of input. Or you could add a check for a blank line:

while (<>) {
   chomp;
   last if $_ eq "";
   print grep /\b$_\b/s, @lines;
}

Answer 2

There is possible problem in your example with my @match = grep {/\\b$_\\b/s} @lines; as grep is not working with user input, but only with content of @lines . What it does is this:

grep { $lines[index] =~ /\b$lines[index]\b/s }

and you probably want this:

while (my $input = <>) {
  chomp($input);
  last if $input =~ /^ \s* $/x; # exit loop if no input or only whitespaces

  my @match = grep { /\b$input\b/s } @lines;
  print @match;
}