bash - Finding a file by md5sum

Given the md5sum of a file, I want to know if anywhere else in the directory tree is another file with the same md5sum (but maybe under a different name). How can I do that in bash?

P.S.: To emphasize, this should work for the entire tree below a given directory, i.e. must work recursively not just in the current directory.

Using find to recursively test all files:

find . -type f -exec \
bash -c 'md5sum "$0" | grep -q 2690d194b68463c5a6dd53d32ba573c7 && echo $0' {} \;

Here, md5sum outputs the MD5 sum and the file name. You need to grep it for the actual MD5 sum as there is no switch to have it just output the sum alone.

You can check the MD5 sum much easier with md5 if you're on BSD or OS X:

find . -type f -exec \
bash -c '[ "$(md5 -q "$0")" = 2690d194b68463c5a6dd53d32ba573c7 ] && echo $0' {} \;

Borrowing some of the solution from slhck, I've came up with

find . -type f -print0 | while read -r -d '' f;
do
 md5sum "$f" | grep "$1"
done

Where $1 is the first argument. If you want to check for a missing argument start the file with:

if [ -z "$1" ]
  then
    echo "No argument supplied"
    exit
fi

The other solutions are good but I want to propose one with fewer spawned processes, which should be significantly faster for many small files, if you have GNU find:

find /path/to/tree -type f -exec md5sum \{\} + | sed -nre 's/^md5-to-search-for  //p'

or without GNU find:

find /path/to/tree -type f -print0 | xargs -r -0 -- md5sum | sed -nre 's/^md5-to-search-for  //p'