Macos – Using find in macOS terminal with regex

findmacosregexterminal

I'm trying to search a folder containing variations on different image filenames:

1_2-300x224.jpg
1_2-600x449.jpg
1_2-600x600.jpg
1_2-768x575.jpg
1_2-802x600.jpg
1_2.jpg

The plan is to find and delete the files ending in 2-4 digits + 'x' + 2-4 digits. I can create this match on Regexr using the expression .*(\d{2,4}x\d{2,4}).jpg (this expression highlights everything except for 1_2.jpg).

However, running find . -name ".*(\d{2,4}x\d{2,4}).jpg" returns no results.

I'm flummoxed!

Best Answer

There are a couple of issues here. Firstly, as John mentioned, -name does sub-string matching with globs, you need to use -regex, and secondly, there are regular expression dialect incompatibilities. By default GNU find uses Emacs regular expressions and BSD find uses posix-basic regular expressions. If you have find.info installed you can read more about it here:

info find.info 'Reference' 'Regular Expressions' 'emacs regular expression'

Supported regular expression dialects can be found here:

info find.info 'Reference' 'Regular Expressions'

Here:

* findutils-default regular expression syntax::
* emacs regular expression syntax::
* gnu-awk regular expression syntax::
* grep regular expression syntax::
* posix-awk regular expression syntax::
* awk regular expression syntax::
* posix-basic regular expression syntax::
* posix-egrep regular expression syntax::
* egrep regular expression syntax::
* posix-extended regular expression syntax::

GNU find

You can make your expression work with posix-extended like this with GNU find:

find . -regextype posix-extended -regex '.*[0-9]{2,4}x[0-9]{2,4}.jpg'

Output:

./1_2-600x600.jpg
./1_2-802x600.jpg
./1_2-600x449.jpg
./1_2-300x224.jpg
./1_2-768x575.jpg

BSD find

I don't have access to BSD find, but I think this should work:

find -E . -regex '.*[0-9]{2,4}x[0-9]{2,4}\.jpg'

Related Solutions

Excel – How find & replace using wildcards with regex substitution

There is an add-on at www.codedawn.com that adds regexp functionality to MS Excel's find&replace dialog. That's the answer! Just one note: replacements made by this add-on are NOT UNDOABLE. You will be warned to save your workbook before committing replace.

Use of the “OR” Regex operator with the find command

Reading into the man page of find gives a bit of useful information:

The regular expressions understood by find are by default Emacs Regular Expressions.

So, taking a look into the syntax of Emacs Regex

It seems that all special characters are required to be escaped with \. Taking this into account, the expected results were obtained after changing the regular expression to the following:

find /path/to/images/ -regex ".*\(26[2-7]\|27[0-2]\).*" -exec echo {} \;

I consulted the man page before posting this question, but apparently not meticulously enough.