in reply to Unwanted interpolation in backquoted string

You should escape the "$2" with backslashes otherwise it gets interpolated by perl.

A better way? Umm, that depends on the point of view. To me, a better way is a perl only way to minimize dependency on external programs and platform independent as well. So instead of using external programs, I would do it in perl.

use IO::File;

...

my $good = getvalue($file, $vals[0]);

...

sub getvalue
{
  my ($file, $val) = @_;
  my $val;

  my $f = new IO::File $file, "r" or die "Can not open file";
  while (my $line = <$f>) {
    if ($line =~ /$val/) {
       return (split /,/, $line)[1]; # return 2nd field
    }
  }
  return undef;
}

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Re: Re: Unwanted interpolation in backquoted string
by graff (Chancellor) on May 04, 2004 at 12:00 UTC
    Your "pure-perl" alternative is not exactly equivalent to the OP. First, by default "awk" splits on white-space, just like the default behavior of "split" (so you shouldn't be splitting on commas). Second, if "$file" contains multiple lines that match $vals[0], the OP's backtick version will return a string with multiple lines, whereas your code will only return at most a single line. (Oh, and why do you have "my $val" a second time?) To replicate the "grep | awk" pipeline properly, the sub would actually be simpler: 
    sub getvalue
{ 
   my ($file, $val) = @_;

   my $f = new IO::File $file, "r" or die "Can not open $file: $!";
   my $matched = '';

   while (<$f>)
   {
      $matched .= (split)[1] . "\n" if (/$val/);
   }
   return $matched;
}

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[d/l]
[select]
      Or even simpler. 
      $good = do {
    local @ARGV = ($file);
    join '', map { /$vals[0]/i ? (split)[1]."\n" : () } <>;
};

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[reply]
[d/l]
      I was just giving an idea on how this could be done, not on the absolute correctness of the code though.

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Re: Re: Unwanted interpolation in backquoted string
by mhearse (Chaplain) on May 04, 2004 at 06:44 UTC
    Ahhh. Of course. Thanks much.
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