diff options
Diffstat (limited to 'admin/notes/exit-value')
-rw-r--r-- | admin/notes/exit-value | 43 |
1 files changed, 18 insertions, 25 deletions
diff --git a/admin/notes/exit-value b/admin/notes/exit-value index cad6862c8a..96337e4c8d 100644 --- a/admin/notes/exit-value +++ b/admin/notes/exit-value @@ -1,35 +1,28 @@ 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>. |