The docs say this:

'-batch'
     Run in batch mode.  Exit with status '0' after processing all the
     command files specified with '-x' (and all commands from
     initialization files, if not inhibited with '-n').  Exit with
     nonzero status if an error occurs in executing the GDB commands in
     the command files.  Batch mode also disables pagination, sets
     unlimited terminal width and height see Screen Size, and acts
     as if 'set confirm off' were in effect (see Messages/Warnings).

bash$ gdb -batch -ex foo
Undefined command: "foo".  Try "help".
bash$ echo $?
0