How to use regex with find command?

Question

I have some images named with generated uuid1 string. For example 81397018-b84a-11e0-9d2a-001b77dc0bed.jpg. I want to find out all these images using "find" command:

find . -regex "[a-f0-9\-]\{36\}\.jpg".

But it doesn't work. Is something wrong with the regex?

maybe change the regextype. The default is *Emacs Regular Expressions*, whatever that means. — pavium, Jul 27 '11 at 13:11

score 468 · Accepted Answer · edited Jul 26 '23 at 08:41

468

find . -regextype sed -regex ".*/[a-f0-9\-]\{36\}\.jpg"

Note that you need to specify .*/ in the beginning because find matches the whole path.

Example:

susam@nifty:~/so$ find . -name "*.jpg"
./foo-111.jpg
./test/81397018-b84a-11e0-9d2a-001b77dc0bed.jpg
./81397018-b84a-11e0-9d2a-001b77dc0bed.jpg
susam@nifty:~/so$ 
susam@nifty:~/so$ find . -regextype sed -regex ".*/[a-f0-9\-]\{36\}\.jpg"
./test/81397018-b84a-11e0-9d2a-001b77dc0bed.jpg
./81397018-b84a-11e0-9d2a-001b77dc0bed.jpg

My version of find:

$ find --version
find (GNU findutils) 4.4.2
Copyright (C) 2007 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by Eric B. Decker, James Youngman, and Kevin Dalley.
Built using GNU gnulib version e5573b1bad88bfabcda181b9e0125fb0c52b7d3b
Features enabled: D_TYPE O_NOFOLLOW(enabled) LEAF_OPTIMISATION FTS() CBO(level=0) 
susam@nifty:~/so$ 
susam@nifty:~/so$ find . -regextype foo -regex ".*/[a-f0-9\-]\{36\}\.jpg"
find: Unknown regular expression type `foo'; valid types are `findutils-default', `awk', `egrep', `ed', `emacs', `gnu-awk', `grep', `posix-awk', `posix-basic', `posix-egrep', `posix-extended', `posix-minimal-basic', `sed'.

edited Jul 26 '23 at 08:41

Benjamin Loison

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answered Jul 27 '11 at 13:32

Susam Pal

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I don't know if this is just my version but I get `find: Unknown regular expression type sed; valid types are findutils-default, awk, egrep, emacs, gnu-awk, grep posix-awk, posix-basic, posix-egrep, posix-extended` – yarian Jul 27 '11 at 13:36
My version is find (GNU findutils) 4.4.2 – thoslin Jul 27 '11 at 13:37
4

@Tom it's the way regex in find works. According to the man page, the regex matches the whole file path, directories included, which means there's an implicit `"^ ... $"` surrounding your regex. It must match the WHOLE result line. – Manny D Jul 27 '11 at 13:40
Manny, I think Tom is wondering why `-regextype sed` is the only thing that seems to work. AFAIK, `-regextype egrep` should also work because `egrep` supports repetition counts but for some reason it doesn't. – Susam Pal Jul 27 '11 at 13:41
using find (GNU findutils) 4.5.10 it works here without regextype – andrej Nov 04 '12 at 22:26
3

I don't think you need the `/` in `.*/` because `.*` matches zero or more of (almost) any character. – Jeff Feb 16 '13 at 01:05
3

For those (like me) who didn't read the regex properly first time: Note the backslashes preceding special regex characters, e.g.: `\{36\}` – Lucas Wilson-Richter Sep 24 '13 at 00:45
If U use Mac OSX check `'-E'` and `'-regex'` out. Here is example. `find -E . -regex ".*\/[a-f0-9\-]{36}\.png"` `-E` is equivalent with `-regextype egrep` – TopChul Jan 27 '14 at 03:16
find . -regextype posix-egrep -regex '.*/[0-9a-z]{32}.jpg' – Codefor Aug 23 '14 at 09:19
19

I had trouble finding the full list of regex types (manpage is not up to date): `valid types are 'findutils-default', 'awk', ' egrep', 'ed', 'emacs', 'gnu-awk', 'grep', 'posix-awk', 'posix-basic', 'posix-egrep', 'posix -extended', 'posix-minimal-basic', 'sed'.` – Noah Sussman Jul 30 '15 at 17:02
I found ...\{36\}... to work with the following regextypes: ed, grep, posix-basic, posix-minimal-basic, sed. – Gerald Schade Mar 11 '17 at 09:32
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So `-name` cannot be used with regular expressions in `find`? – Melab Jul 05 '17 at 15:05
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Make sure to put the `-regextype` flag *before* the `-regex` flag, otherwise it does not apply! – Christopher Orr Dec 04 '17 at 20:55
2

@osullic I got the list of valid regex types by running `find -regextype help` – Noah Sussman Feb 19 '20 at 18:41
Doesn't work on mac: `find: -regextype: unknown primary or operator` – Caleb Stanford Aug 23 '22 at 17:24
@CalebStanford This is why I often install the GNU version of the command line tools. In this case you can do `brew install findutils` which installs `find` as `gfind`. I believe you can also do `brew install findutils --with-default-names` but you will have to ensure the GNU version is first in your `PATH` environment variable. – steveb Jul 12 '23 at 00:00

score 119 · Answer 2 · edited Jul 26 '23 at 08:41

119

The -regex find expression matches the whole name, including the relative path from the current directory. For find . this always starts with ./, then any directories.

Also, these are emacs regular expressions, which have other escaping rules than the usual egrep regular expressions.

If these are all directly in the current directory, then

find . -regex '\./[a-f0-9\-]\{36\}\.jpg'

should work. (I'm not really sure - I can't get the counted repetition to work here.) You can switch to egrep expressions by -regextype posix-egrep:

find . -regextype posix-egrep -regex '\./[a-f0-9\-]{36}\.jpg'

(Note that everything said here is for GNU find, I don't know anything about the BSD one which is also the default on Mac.)

edited Jul 26 '23 at 08:41

Benjamin Loison

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answered Jul 27 '11 at 13:27

Paŭlo Ebermann

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I had parenthesis for multiple matching strings in my regex, so the `posix-egrep` type worked for me. – palswim Jan 10 '14 at 18:36
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Something to note, `-regextype` is an option for GNU `find` and not BSD (at least not Mac BSD-like) `find`. If this option is not available, be sure to install GNU find. If on a Mac that's possible with the brew package `findutils`. Find is then available via `gfind`. – DanCat Oct 10 '16 at 03:02
regextype posix-egrep did the task for me. I think the default is regextype emacs. – infoclogged Jan 11 '19 at 19:17
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`posix-egrep` can be shortened to just `egrep` – bloody Nov 11 '21 at 09:32

score 54 · Answer 3 · answered Jul 27 '11 at 13:33

54

Judging from other answers, it seems this might be find's fault.

However you can do it this way instead:

find . * | grep -P "[a-f0-9\-]{36}\.jpg"

You might have to tweak the grep a bit and use different options depending on what you want but it works.

answered Jul 27 '11 at 13:33

yarian

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Worked well for me and provides a great degree of freedom with respect to the regex. – glaucon Oct 31 '14 at 01:56
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A downside with this is that you can't take advantage of `find`'s `-prune` functionality which will skip over certain directories altogether. Most often this isn't really important, but it is worth mentioning. – Alexander Bird Feb 09 '16 at 21:35
-prune will still work, I guess. It would be more dangerous to use -exec - it would run on all files and not just those that grep allows to pass. – tpb261 Apr 14 '20 at 12:04
2

`find . *` is an equivalent of `find` (shorter command). – bloody Nov 10 '21 at 17:13
1

Thanks! I was scratching my head with `find`'s syntax for regex but this did the trick. – uzluisf Aug 05 '23 at 15:38

score 31 · Answer 4 · edited Jul 26 '23 at 08:41

31

on Mac OS X (BSD find): Same effect as the accepted answer.

$ find -E . -regex ".*/[a-f0-9\-]{36}.jpg"

man find says -E uses extended regex support

NOTE: the .*/ prefix is needed to match a complete path:

For comparison purposes, here's the GNU/Linux version:

$ find . -regextype sed -regex ".*/[a-f0-9\-]\{36\}\.jpg"

edited Jul 26 '23 at 08:41

Benjamin Loison

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answered Aug 31 '18 at 23:33

Stan Kurdziel

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Seems `-E` is not available on Ubuntu (tested on WSL Ubuntu) – Elliott Beach Feb 08 '19 at 12:06
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@Clever Little Monkey - No, the accepted answer should work on Ubuntu, this variation is for Mac OS X specifically (or perhaps another BSD variant like FreeBSD) – Stan Kurdziel Feb 10 '19 at 07:52
The `-E` option is not available on the OpenBSD version of find – moo Mar 31 '22 at 19:16

score 15 · Answer 5 · edited Jul 26 '23 at 08:41

15

Simple way - you can specify .* in the beginning because find matches the whole path.

$ find . -regextype egrep -regex '.*[a-f0-9\-]{36}\.jpg$'

find version

$ find --version
find (GNU findutils) 4.6.0
Copyright (C) 2015 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later 
<http://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by Eric B. Decker, James Youngman, and Kevin Dalley.
Features enabled: D_TYPE O_NOFOLLOW(enabled) LEAF_OPTIMISATION 
FTS(FTS_CWDFD) CBO(level=2)

edited Jul 26 '23 at 08:41

Benjamin Loison

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answered Apr 17 '18 at 11:32

binbjz

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**you can specify .* in the beginning because find matches the whole path.** that is a very tricky good point . if you were at `dir/` and searchs for `samplefile.txt` with this notation `find . -regex 'samplefile.*' ` find wont work – Elcid Feb 04 '21 at 07:31
I do prefer `egrep` to `sed` - so thanks – dotnetCarpenter Dec 20 '21 at 15:44

score 15 · Answer 6 · edited Jul 26 '23 at 08:42

15

Try to use single quotes (') to avoid shell escaping of your string. Remember that the expression needs to match the whole path, i.e. needs to look like:

find . -regex '\./[a-f0-9-]*.jpg'

Apart from that, it seems that my find (GNU 4.4.2) only knows basic regular expressions, especially not the {36} syntax. I think you'll have to make do without it.

edited Jul 26 '23 at 08:42

Benjamin Loison

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answered Jul 27 '11 at 13:26

thiton

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score 11 · Answer 7 · edited Jul 26 '23 at 08:42

You should use absolute directory path when applying find instruction with regular expression. In your example, the

find . -regex "[a-f0-9\-]\{36\}\.jpg"

should be changed into

find . -regex "./[a-f0-9\-]\{36\}\.jpg"

In most Linux systems, some disciplines in regular expression cannot be recognized by that system, so you have to explicitly point out -regexty like

find . -regextype posix-extended -regex "[a-f0-9\-]\{36\}\.jpg"

score 1 · Answer 8 · answered Mar 31 '22 at 19:27

If you want to maintain cross-platform compatibility, I could find no built-in regex search option that works across different versions of find in a consistent way.

Combine with grep

As suggested by @yarian, you could run an over-inclusive find and then run the output through grep:

find . | grep -E '<POSIX regex>'

This is likely to be slow but will give you cross-platform regex search if you need to use a full regular expression and can't reformat your search as a glob

Rewrite as a glob

The -name option is compatible with globs which will provide limited (but cross-platform) pattern matching.

You can use all the patterns that you would on the command line like * ? {} **. Although not as powerful as full regex, you might be able to reformulate your search to globs depending on your use-case.

Internet search for globs - many tutorials detailing full functionality are available online

score 1 · Answer 9 · answered May 30 '22 at 03:11

One thing I don't see covered is how to combine regular expressions with regular find syntax.

Eg: I want to find core dump files on BSD / Linux, I change to the root I want to scan.. eg: cd / then execute:

find \( -path "./dev" -o -path "./sys" -o -path "./proc" \) -prune -o -type f -regextype sed -regex ".*\.core$" -exec du -h {} \; 2> /dev/null

So I am using the prune command to exclude multiple system directories, before doing regular expression on the remaining files. Any error output (stderr) is deleted.

The important part is to use the Find syntax first, then OR (-o) with the regular expression.

How to use regex with find command?

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