Shell – find utility does not recognize bracket notation

The problem is that the default type of regex's used by find is emacs-style. Find's documentation for emacs style regexes doesn't include the \{n,\} construction--leading me to believe that it isn't supported in find's implemenation of emacs-style regular expressions. The emacs-wiki lists this as valid, however it is possible that this wasn't always the case.

I found that your regex produced output if you do this:

$ find . -regextype posix-basic -regex '.*\..\{5,\}'

The parameter passed to -name is a filesystem glob pattern, the same as the you'd enter for other commands, such as ls -l *in.

For each file it finds it compares the basename of the file to the pattern you passed. So when it finds /bin/foobar it compares foobar to *in, doesn't match, skips; but with /bin/login it compares login to *in and this does match, and so prints.

Now you need to be careful because *in might be matched on the command line depending on files in the current directory.

So, for example:

$ find /bin -name *in
/bin
/bin/login

$ touch foobarin

$ find /bin -name *in
$ 

Notice the same find command returned two different results.

We can see why if we set the shell to debug mode:

$ rm foobarin 

$ set -x

$ find /bin -name *in
+ find /bin -name '*in'
/bin
/bin/login

$ touch foobarin     
+ touch foobarin

$ find /bin -name *in
+ find /bin -name foobarin

$ 

The lines starting with a + are what the shell interpreted the command entered. We can see that the second find command expanded the *in to match the existing filename.

Because of this it's recommended to quote names

$ find /bin -name '*in'
+ find /bin -name '*in'
/bin
/bin/login