grep whole words made of only uppercase letters

Question

Seems like this is rather simple, but I\'m having trouble.

I have a text document that looks, for example, like this:

This is a
TEXT DOCUME

Answer 1

The example output shows multiple space separated uppercase words on the same line, which can be achieved with

$ grep -ow '[[:upper:]][[:upper:][:space:]]*[[:upper:]]' infile
TEXT DOCUMENT
SOME
BUT NOT
ALL CAPS

Any sequence starting and ending with an uppercase character, and uppercase characters or whitespace between them. -o returns the matches only, and -w makes sure that we don't match something like WORDlowercase.