How can I utilize PCRE and named capture groups from Bash such that I can export variables back to the parent environment?

Question

Is it possible to invoke a program such as Perl from a Bash script to perform a regex with named capture groups and export the results as variables back to the parent shell?

For example:

#!/bin/bash

input="a small box"
regex="a (?P<size>\w+) box"

perl -e "
my \$str = \"$input\";

if ( \$str =~ /$regex/ ) {
   # Do a thing...
}
"

# Illustrative purposes only
echo $size

The expected output would be small .

This doesn't have to be done with Perl specifically. I just want to know if this can be done and demonstrated.

I have a few thousand files to parse and need to build a very large and complex regular expression to handle their contents. While this can be done with other tools such as pcregrep or =~ with numbered capture groups, I would prefer to use named capture groups for clarity.

I don't feel that I need to use anything other than Bash except for the heavy lifting of this complex regular expression. Is there a way to easily drop into another language to take advantage of named capture groups and export the result back to the parent environment?

Answer 1

There is no way to export a variable from a subprocess to a parent process.

The closest to that would be child process giving output in a way that a bash shell can evaluate. Eg if your perl program would output

export LEGS=3
export ANIMAL='Lame boar'

then you can invoke it from bash like this:

eval $(perl animal.pl)

and those variables would be inserted into your environment:

echo "$ANIMAL has $LEGS legs."

EDIT: With Ruby, assuming input and regex are defined,

eval $(ruby -r shellwords -e "
if (match = ENV['input'].match(ENV['regex']))
  match.names.each do |name|
    puts %{export #{name}=#{Shellwords::shellescape(match[name])}}
  end
end
")