| 123456789101112131415161718192021222324252627282930313233343536 |
- 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 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.]
|
