What does WEXITSTATUS(status) return?
c, fork, posix, signals, unix
Solution
`WEXITSTATUS(stat_val)` is a macro (so in fact it does not "return" something, but "evaluates" to something).
For how it works you might like to look it up in the headers (which should be `#include`d via `<sys/wait.h>`) that come with the C-compiler you use.
The implementation of this macro might differ from one C-implementation to the other.
Please note, that this macro only gives a sane value, if the macro `WIFEXITED(stat_val)` gave you a value unequal to `0`.
Verbatim from `waitpid()`'s POSIX specification:
WEXITSTATUS(stat_val)
If the value of WIFEXITED(stat_val) is non-zero, this macro evaluates to the low-order 8 bits of the status argument that the child process passed to _exit() or exit(), or the value the child process returned from main().
The motivation behind adding up the return code(s?) of a particular program is only known to the code's author and the hopefully existing documentation.
Problem
I am trying to understand how `WEXITSTATUS(status)` works. I have come across a piece of code where the return value of `WEXITSTATUS(status)` is being added to a variable. Here is the snippet: ``` waitpid(-1, &status, 0); counter += WEXITSTATUS(status); ``` How can the return value of `WEXITSTATUS` be calculated?