How to grep only words which consist of capital characters

Question

I have problem write grep which should grep only those lines, in which is word that consist only from capital characters.

For example I have file : file1.txt

Abc AAA
ADFSD
F
AAAAx

And output should be :

Abc AAA
ADFSD
F

Thank for any advice.

Answer 1

You can just use:

grep -E '\b[[:upper:]]+\b' file1.txt

That is, look for whole words composed of only uppercase letters.

Answer 2

This egrep should work:

egrep '\b[A-Z]+\b' file

Answer 3

This will produce the desired results,

egrep '\b[A-Z]+\b'  file1.txt

Results are

Abc AAA
ADFSD
F

Answer 4

GNU grep supports POSIX patterns, so you can simply do:

grep -e '[[:upper:]]' file1.txt