Regular Expression in Find command

Question

I want to list out the files which starts with a number and ends with ".c" extension. The following is the find command which is used. But, it does not give the expected output.

Command:

find -type f -regex "^[0-9].*\\.c$"

Solution 1

It's because the regex option works with the full path and you specified only the file name. From man find:

   -regex pattern
         File name matches regular expression pattern.  This is a match on the whole
         path, not a search.  For example, to match a file named './fubar3', you can use
         the  regular  expression  '.*bar.'  or  '.*b.*3',  but  not 'f.*r3'. 
         The regular expressions understood by find are by default Emacs Regular
         Expressions, but this can be changed with the -regextype option.

Try with this:

find -type f -regex ".*/[0-9][^/]+\.c$"

where you explicitly look for a string where "the format of your filename follows any string that terminates with a slash"

UPDATE: I made a correction to the regex. I changed .* in the filename to [^\]+ as after "any string that terminates with a slash" we don't want to find a slash in that part of the string because it wouldn't be a filename but another directory!

NOTE: The matching .* can be very harmful...

Solution 2

Just use -name option. It accepts pattern for the last component of the path name as the doc says:

-name pattern

         True if the last component of the pathname being examined matches
         pattern.  Special shell pattern matching characters (``['',
         ``]'', ``*'', and ``?'') may be used as part of pattern.  These
         characters may be matched explicitly by escaping them with a
         backslash (``\'').

So:

$ find -type f -name "[0-9]*.c"

should work.

Comments

[knittl]

. matches any character. Try [.] or \. Also, -regex matches the full path, not the filename.

[Mohan]

I already try this. But it does not work

[DBedrenko]

@Mohan As knittl said find doesn't print just the filename, so something like this would work: find -type f -regex '^[.][/][0-9].*.c'

[Mohan]

This also does not give expected output. Because "./<directory name>/..../<filename>". You syntax will work only when the command executed within the same directory. for recursive search the following is the command which gives expected output. find -type f -regex ".*/[0-9].*\.c$".

[twalberg]

You could dispense with the regex here, as it seems to be complicating things, and just use a glob pattern, as in find -type f -name '[0-9]*.c'...