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Starnec
Asked: 2024-10-02 21:51:23 +0800 CST

Find command with -regex option using caret have unexpected behaviour

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I would like to run the find command and get some of the files/directories in the desktop directory using regex option of the command with the symbol caret ^

As you know the caret ^ matches the beginning of a line, and I would like to get all the files/directories starting with the letter t; I used the following command find . -regex "^./t", but as it turned out, it will only match the file/folder whose name is a simple t!

I know that the regex will match the whole path and not only the file name. But why all of these do not match since they start with ./t.

./tcpdump.txt
./t.txt
./test.sh
./trade.txt
./torbrowser.desktop
./token.txt

PS: This regex worked for me, ^./t.*, but still unable to understand the behavior of caret in the original command

command-line

2 Answers

  1. The fact that the regex always matches the whole path means the caret and dollar sign are redundant: The whole path must match, not just its substring. Or, you can always imagine the regex starts with a caret and ends with a dollar sign, even if you don't type them.

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  2. Best Answer

    The -regex option expects a pattern that matches the entire path. See 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.

    The caret is pointless in this context since as explained above, the -regex will have to match everything, so essentially, the ^ and $ are implied.

    You gave it ^./t which means "look for any character" (remember that the . means "any character" in regular expressions, it doesn't mean a literal .) followed by a / and then the single letter t and nothing else.

    What you need here is the -name operand, which takes globs and not regular expressions, and only matches the file's name, not the entire path. So to find all files/dirs whose name begins with a t, use:

    find . -name "t*"

    The glob t* means "t followed by 0 or more characters". If you really want to do it with -regex, although that only makes it more complicated, you would need to specify that you allow anything to come after the t, like this:

    find . -regex '.*/t.*'

    That regex means "match as many characters as you can (including 0) until the last / and then a t followed by anything else.

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