re.search() in python goes into an infinite loop

Question

I'm trying to extract file paths (Windows/Ubuntu, relative/absolute) from a text document.

The regular expression code below is used check if a word is a file path or not.

It works for most of the cases but fails for one case, where it goes into an infinite loop. Any explanation for this?

import re
path_regex = re.compile(r'^([\.]*)([/]+)(((?![<>:"/\\|?*]).)+((?<![ .])(\\|/))?)*$' , re.I)
text = '/var/lib/jenkins/jobs/abcd-deploy-test-environment-oneccc/workspace/../workspace/abcd-deploy-test-environment.sh'
path_regex.search(text)

Answer 1

Indeed there is a problem.
You have overlayed subexpressions mixed with spurious quantifiers.

modified for required parts between slashes
It is easily fixed using this ^([\.]*)([/]+)((?:[^<>:"/\\|?*.\r\n]|\.(?![\\/]))[\\/]?)*$

The idea is to see just what your guarding against.
The guard is that you'd allow forward or back slash if not preceeded by a dot.

So, you have to include the dot in the exclusion class with the \ and /
then qualify them in a separate alternation.

If you do it this way, it will always pass.

 ^ 
 ( [\.]* )                     # (1)
 ( [/]+ )                      # (2)
 (                             # (3 start)
      (?:                           # Group start (required between slashes)
           [^<>:"/\\|?*.\r\n]            # Any character, but exclude these
        |                              # or,
           \.                            # The dot, if not followed by forward or back slash
           (?! [\\/] )
      )                             # Group end
      [\\/]?                        # Optional forward or back shash
 )*                            # (3 end)
 $