I am trying to parse some output from a command, I want to check if the command had an error in it, so I look for the string **Apply Error**. If there is no error present the previously mentioned string is absent. My regex to match that is (?s)Ran Apply. ?(\*\*Apply Error\*\*)?. I am doing this in Golang

This regex does not work even when the string ** Apply Error** is present in the output, if I remove the last ? in my regex it works as expected. It captures 2 groups with the second being the optional part.

Examples: Case - 1 when the string **Apply Error** is present

Ran Apply for dir: `some random path/something/something`

`**Apply Error**`

Output: Match **Apply Error** and capture it as a group

Case - 2 When **Apply Error** is not present

Ran Apply for dir: `some random path/something/something`
some random text

Output: Match everything as is

Demo: https://regex101.com/r/Um3CNc/1 In the demo even though ** Apply Error** is present it does not match it

How can I match the optional part?

CodePudding user response：

You can use

(?s)Ran Apply\b(?:. ?(\*\*Apply Error\*\*)|.*)

Explanation

• (?s) Inline modifier to have the dot match a newline
• Ran Apply\b Match literally followed by a word boundary
• (?: Non capture group
• . ?(\*\*Apply Error\*\*) Match 1 chars, as few as possible and capture **Apply Error** in group 1
  • | Or
  • .* Match the rest of the text
• ) Close non capture group

See a regex demo with Apply Error present and without Apply Error present.