Regex validation of folder path with unknown depth of nested directories

Question

I have a simple regex ^\\{2}[a-z0-9?_?]*\\{1}[a-z0-9?_?]*$ that can validate folder paths of the type \\foo_bar1\foo_bar_2.

The problem is that the complete path is created by the user using a form and it is unknown how deep the user might want to nest directories. Regardless, I want to make sure that the path is validated, for example, the user might want to create a path like \\foo_bar1\foo_bar_2\foo_bar_3\foo_bar_4\foo_bar_n.

Is there a way I can generalize the \\{1}[a-z0-9?_?]* part of the regex for the above problem for n number of nested directories?

What did you try to achieve with ?_?? Looking at your example I guess ^\\\\\w+(?:\\\w+)*$ will work. — JvdV
– JvdV, Commented Aug 23, 2021 at 6:24
?_? numbers and underscores can be optional in the folder path, however no other special characters — foobar
– foobar, Commented Aug 23, 2021 at 6:26
Then the given regex would work I guess since \w is shorthand for [A-Za-z0-9_]. — JvdV
– JvdV, Commented Aug 23, 2021 at 6:28
@JvdV yes, just tested, it works perfectly, what is ?: doing though? also, if you feel like it, could you please write a short answer and I can accept it :) thanks — foobar
– foobar, Commented Aug 23, 2021 at 6:34

JvdV · Accepted Answer · 2021-08-23 06:42:28Z

1

If you are looking to find a pattern that would accept alphanumeric characters and underscores, you could simply make use of the \w+ shorthand to match any word-character:

^\\\\\w+(?:\\\w+)*$

See an online demo:

^ - Start-line anchor.
\\\\ - Two escaped (therefor literal) backslash characters.
\w+ - 1+ Word-characters.
(?: - Open a non-capture group:
- \\\w+ - A single literal backslash (\\) followed by 1+ word-characters (\w+).
- )* - Close non-capture group and match it 0+ times.

answered Aug 23, 2021 at 6:42

JvdV

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