xargs does all the magic:
find . -name test -type d -print0|xargs -0 rm -r --
xargs executes the command passed as parameters, with the arguments passed to stdin.
This is using rm -r to delete the directory and all its children.
The -- denotes the end of the arguments, to avoid a path starting with - from being treated as an argument.
-print0 tells find to print \0 characters instead of newlines; and -0 tells xargs to treat only \0 as argument separator.
This is calling rm with many directories at once, avoiding the overhead of calling rm separately for each directory.
As an alternative, find can also run a command for each selected file:
find . -name test -type d -exec rm -r {} \;
And this one, with better performance, since it will call rm with multiple directories at once:
find . -name test -type d -exec rm -r {} +
(Note the + at the end; this one is equivalent to the xargs solution.)
You have already provided a find command that is safe for oddly named files:
find -regextype posix-egrep -type f -regex '.*[^/]{5}' -delete
This regex matches five trailing characters that do not contain a slash (i.e. the filename is longer than five chars).
The Bash loop you provided will generally work, but it probably does not scale with thousands of files and may break with special filenames.
An alternative that is similar in efficiency, but may provide more flexibility (replace rm by -n1 echo to print all files):
find -type f -print0 | grep -Ez '[^/]{5}$' | xargs -0 rm
The -print0, -z and -0 options ensure that each file name is terminated with a NUL byte. This ensures that special characters do not split filenames (newlines break the Bash command you provided). Although this grep command still fails with a name such as path/abc\ndef (where \n is a newline), it won't be split up into path/abc and def.
As you will rarely find files with \n in their name, I leave the implementation for that case as an exercise to the reader.
Best Answer
The syntax is a little bit tricky:
find ./directory -name "*.srt" -exec rm {} \;