BOSS KEAN: Sorry, Luke, I’m just doing my job. You gotta appreciate that.
LUKE: Calling it your job don’t make it right, Boss.

Donn Pearce (1928-2017) American novelist, screenwriter

Cool Hand Luke (1967) [with Frank Pierson]

In the actual final script, the exchange goes:

BOSS KEAN: Ah'm jus' doin' mah job, Luke. You gotta appreciate that.
LUKE: Boss, when you do somethin' to me you better do it because you got to or want to ... but not because it's your damn job.