What does the -b option do when using the `at` command, if anything?

Question

According to man at, one of the ways to call at (version 3.1.10 on my system) is with the form:

at [-V] [-q queue] [-f file] [-mldbv] time

Although -m, -l, -d, and -v are all documented, nowhere can I find an explanation as to how the -b flag is actually used. My original intuition was that it might allow access to batch, similar to the -l and -d options, which provide alternate ways to access atq and atrm respectively.

On attempting to test this theory to see if it would just put a job into the "b" queue that batch uses, I tried running at -b now + 1 hour, but this fails right away with:

at: invalid option -- 'b'

Perhaps -b only works when given with certain other options, or perhaps I'm misinterpreting the man-pages somehow. Any insights into this?

Answer 1

at -b is supposed to be equivalent to batch, but there's a bug: b isn't declared in the list of valid options, so getopt() reports an error and -b isn't actually processed.

If you add b to the list of options, then it's handled correctly and at -b becomes equivalent to batch.