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
+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. This is
+not always the case on other systems.
+
+From the point of view of the program stdlib.h provides macros
+`EXIT_SUCCESS' and `EXIT_FAILURE' that should DTRT. N.B. 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
+ #ifdef WEIRD_OS
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 are tricky, but 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.
-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.]
+[Insert ZAMM quote here.] <-- I presume this refers to ``Zen and the
+Art of Motorcycle Maintenance'' - Reuben Thomas <rrt@sc3d.org>.