How to replace a token with an increase in number in Perl?

Question

I want to replace a token in a text file with a number. The " <count>" sign , and I want it to be replaced by the number of samples so far. For example:

This <count> is a <count> count.
The <count> count increases <count><count><count>.
<count><count><count><count><count><count>

becomes:

This 1 is a 2 count.
The 3 count increases 456.
789101112

I'm not sure how to do this, maybe with some loop?

my $text = (the input from file, already taken care of in my script);
my $count = 1;
while( regex not found? )
{
    $text =~ s/<count>/($count);
    $count ++;
}

Answer 1

my $text = "whatever";
my $count = 1;
$text =~ s/<count>/$count++/ge;

should do it for you. The value of / e at the end of the substitution makes a difference.

Answer 2

Here is a procFilescript that does what you requested:

$val = 1;                         # Initial change value.
while (<STDIN>) {                 # Process all lines.
    chomp;                        # Remove linefeed.
    $ln = $_;                     # Save it.
    $oldln = "x" . $ln;           # Force entry into loop.
    while ($oldln ne $ln) {       # Loop until no more changes.
        $oldln = $ln;             # Set lines the same.
        $ln =~ s/<count>/$val/;   # Change one occurrence if we can.
        if ($oldln ne $ln) {      # Increment count if change was made.
            $val++;
        }
    }
    print "$ln\n";                # Print changed line.
}

Run it using cat inputFile | perl procFileand your sample file:

This <count> is a <count> count.
The <count> count increases <count><count><count>.
<count><count><count><count><count><count>

generates:

This 1 is a 2 count.
The 3 count increases 456.
789101112

Answer 3

.

\G, , .

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

my $count = 1;   # start at 1; 

while ( my $line = <STDIN> ) {                            # read stdin 
    while ( $line =~ /\G.*?(<count>)/g ) {                 # scan left to right and pick out one <count> at a time.
        substr( $line, $-[1], $+[1] - $-[1], $count++ );  # replace the substring and increment
    }
    print $line;
}

Its functionally is almost identical to the hosted regex-eval solution, it just works without eval. I previously posted some anti-emergency fear, but its just FUD from other smaller languages ​​did not do eval safely.

The / e effect effectively does this:

replace_callback( \$input, $regex, sub{ 
   return $count++;
}); 

(where replacing the callback is some bloated function that does all the work)

What is really safe, like eggs, its simply not obvious that it is safe.