grep for words of no more than a certain length

Question

I'm looking for a way to grep things like: i log for E M, i 1 f x i 0, I xi 1, 3 1,. simply based on number of characters.

Nothing in that hypothetical output is longer than three characters. This hypothetical one-liner would look something like, grep -v [:alnum:] > {3}. (Except I just don't know how to write that in grep syntax.)

Answer 1

grep -o -w '\w\{1,3\}' data

Options are:

• -o (a GNU extension) prints only matched words
• -w (an extension from BSD, but now widely supported) matches only whole words.

It matches only words (in grep, \w (a GNU extension) short for standard [[:alnum:]_] (same as [A-Za-z0-9_] in the C locale)) of length from 1 to 3 (specified by {1,3})