c - Make gdb quit automatically on successful termination?

Question

I use a debugging script that runs several related processes in succession with the debugger. I'm currently using -x to execute several commands automatically (such as run). How can I make gdb quit automatically when the debugged process successfully terminates? Adding a quit command to the command file will cause that command to be handled not just on successful termination, but when errors occur also (when I'd rather take over at that point).

Here's an extract of what's going on:

+ gdb -return-child-result -x gdbbatch --args ./mkfs.cpfs /dev/loop0
GNU gdb (GDB) 7.1-ubuntu
Reading symbols from /home/matt/cpfs/mkfs.cpfs...done.

Program exited normally.
Breakpoint 2 at 0x805224f: file log.c, line 32.
(gdb)

Contents of gdbbatch:

start
b cpfs_log if level >= WARNING

Answer 1

gdb sets $_exitcode when the program successfully terminates. You can make use of that - set it to an unlikely value at the start of your script, and only quit at the end if it has changed:

set $_exitcode = -999
# ...
run
# ...
if $_exitcode != -999
  quit
end

(Setting $_exitcode to an unlikely value is a bit ugly, but it will otherwise not be defined at all if the program doesn't terminate, and there doesn't seem to be any obvious way of asking "is this variable defined?" in a conditional.)