Match optional pattern with find command

Question

I want to match all files with a typical fortran file extension with find. Typical extensions are .f .F .for .FOR .f90 .F90 .f95 .F95 .f03 .F03 .f08 .F08 .f15 .F15 .f18 .F18

what I tried so far is find * -name "*\.[Ff][0-9Oo][0-9Rr]" this works for all the mentioned extensions despite .f and .F. For that I have to make [0-9Oo] and [0-9Rr] optional which is usually done with "?". However, this find * -name "*\.[Ff][0-9Oo]?[0-9Rr]?" does not work with my version of find.

Wiktor Stribiżew · Accepted Answer · 2022-06-29T09:20:04.693

1

With a GNU find, you can use

find * -regextype posix-extended -regex '.*\.[Ff][0-9Oo]?[0-9Rr]?'

The pattern matches a string that fully matches:

.*\. - any text up to the rightmost . including it
[Ff] - F or f
[0-9Oo]? - an optional digit, O or o
[0-9Rr]? - an optional digit, R or r.

You can also use a non-regex approach using mere glob patterns:

find * ( -name "*.[Ff][0-9oO][0-9rR]" -o -name "*.[Ff]" )

Note that here, the * glob pattern matches any text. In the previous solution, it was a quantifier, an operator that makes the preceding pattern match zero or more times. Also, in glob patterns, . matches a literal dot, no need to escape it.

edited Jun 29 '22 at 09:20

answered Jun 29 '22 at 08:48

Wiktor Stribiżew

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Thank you! Is there also a way to achieve the same with the 'findutils-default' regex type? – M0M0 Jun 29 '22 at 08:51
@M0M0 Try `find * -regex '.*\.[Ff][0-9Oo]\{0,1\}[0-9Rr]\{0,1\}'` – Wiktor Stribiżew Jun 29 '22 at 08:52
This one does not work for me. – M0M0 Jun 29 '22 at 08:55
@M0M0 Then forget about using the default flavor. It is broken. – Wiktor Stribiżew Jun 29 '22 at 08:55
ok, can I be sure that -regextype posix-extended will work for all versions of find? – M0M0 Jun 29 '22 at 08:56
@M0M0 I only use Linux. See [How to use regex with find command?](https://stackoverflow.com/q/6844785/3832970) where you can see how this can be "converted" to a MacOS (FreeBSD) `find`. – Wiktor Stribiżew Jun 29 '22 at 09:05
Ok, since I need it to work on MacOS as well, I will probably stay with my less elegant solution: find * \\( -name "*\.[Ff][0-9oO][0-9rR]" -o -name "*\.[Ff]" \\) – M0M0 Jun 29 '22 at 09:17
if you add, that your solution works only for GNU find, I will accept your answer anyway. Thanks again! – M0M0 Jun 29 '22 at 09:18

Match optional pattern with find command

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