Question

I have been trying to write a regular expression for this but so far did not able to succeed.

_ any thing\_ fdfdf \_ any thing_

underscore then any characters until _.

\_ is an escape character so the regular expression must accept string like this.

_ any \_ thing _

the following string:

checking_ happens \_ ano\_ther _ test of bold _ and escape \_asteric

should give:

_ happens \_ ano\_ther _

So far I am only able to come up with this:

(\\_)|_[^_]*[\\_]*[_]

Answer 1

This does the job:

(?<!\\)(?:\\\\)*_((?:[^_\\]|\\.)+)_

Breaking it up:

• (?<!\\)(?:\\\\)* – Match an even number of backslashes not preceded by more backslashes
• _ – followed by an underscore
• ((?:[^_\\]|\\.)+) – Match either of the following 1 or more times
  • [^_\\] – Any character except an underscore or backslash
  • \\. – Any backslash / character pair (e.g. \_ or \\)
• _ – Match the trailing underscore

This will capture the string between the underscores in its first group.