Is it legal to carry a pocket knife into a bar in Texas?

I would imagine that would be OK, as long as you didn't leave it in a patron!

If it is illegal, I am in trouble! [:O]

Yes it's legal as long as it doesn't fit the definition of an illegal knife in TX.

In Texas an "Illegal knife" means a:
(A) knife with a blade over five and one-half inches;
(B) hand instrument designed to cut or stab another by being thrown;
(C) dagger, including but not limited to a dirk, stilletto, and poniard (this generally means two sharpened edges);
(D) bowie knife;
(E) sword; or
(F) spear.

An illegal knife isn't illegal to own, just illegal to carry. This is not to be confused with switchblades, brass knuckles or knuckle duster knives, which are illegal to own (as well as carry).

Carrying an illegal knife will get you up to a year in jail and a $4000 fine. Carrying a knife that is a "prohibited weapon" gets you the same. Carrying either into a bar (or a school, school bus, airport, courthouse, racetrack or polling place on election day)is a felony than get you five in prison and a $10,000 fine.

Don't forget switchblades in your illegal knife list.  BTW "switchblades" include spring-actioned blades, gravity knives, balisongs, and a whole mess of other knives.