So I banged my head against the wall for awhile trying to figure out this simple grep. Essentially, I have a field in a tab delimited file that can take on various forms:

A/T
TA/T
A/TGAC

I just want the lines where the field is [ACTG]/[ACTG], so

A/T - Yes
TA/T - No
A/TGAC - No

So I figured the following would be fine:

grep " [ACTG]\/[ACTG] " file.in > file.out

But I get nothing. Of course if I drop the spaces, I get everything. I've also tried:

grep \s[ACTG]\/[ACTG]\s
grep [:space:][ACTG]\/[ACTG][:space:]
grep \t[ACTG]\/[ACTG]\t

They all return nothing.

Is there something I'm forgetting?

Yes. Word boundaries:
or using the proper grep option:
And welcome to LinuxQuestions!

Thanks, that did it!

Feel like I'm learning a new language and I've got all the big words down and none of the basics :P