patch can produce a variety of messages, especially if it
has trouble decoding its input. In a few situations where it’s not
sure how to proceed,
patch normally prompts you for more
information from the keyboard. There are options to produce more or
fewer messages, to have it not ask for keyboard input, and to
affect the way that file names are quoted in messages.
patch exits with status 0 if all hunks are applied successfully,
1 if some hunks cannot be applied, and 2 if there is more serious trouble.
When applying a set of patches in a loop, you should check the
exit status, so you don’t apply a later patch to a partially patched