mirror of
https://git.savannah.gnu.org/git/emacs.git
synced 2024-11-29 07:58:28 +00:00
36 lines
1.3 KiB
Plaintext
36 lines
1.3 KiB
Plaintext
ttn 2004-05-09
|
|
|
|
The exit value of a program returning to the shell on unixoid systems is
|
|
typically 0 for success, and non-0 (such as 1) for failure. For vms it is
|
|
odd (1,3,5...) for success, even (0,2,4...) for failure.
|
|
|
|
This holds from the point of view of the "shell" (in quotes because vms has a
|
|
different dispatch model that is not explained further here).
|
|
|
|
From the point of view of the program, nowadays stdlib.h on both type of
|
|
systems provides macros `EXIT_SUCCESS' and `EXIT_FAILURE' that should DTRT.
|
|
|
|
NB: The numerical values of these macros DO NOT need to fulfill the the exit
|
|
value requirements outlined in the first paragraph! That is the job of the
|
|
`exit' function. Thus, this kind of construct shows misunderstanding:
|
|
|
|
#ifdef VMS
|
|
exit (1);
|
|
#else
|
|
exit (0);
|
|
#endif
|
|
|
|
Values aside from EXIT_SUCCESS and EXIT_FAILURE are tricky.
|
|
|
|
|
|
|
|
ttn 2004-05-12
|
|
|
|
Values aside from EXIT_SUCCESS and EXIT_FAILURE can be used to indicate
|
|
finer gradations of failure. If this is the only information available
|
|
to the caller, clamping such values to EXIT_FAILURE loses information.
|
|
If there are other ways to indicate the problem to the caller (such as
|
|
a message to stderr) it may be ok to clamp. In all cases, it is the
|
|
relationship between the program and its caller that must be examined.
|
|
[Insert ZAMM quote here.]
|