Hello Sloane,
On 08/04/2016 10:55 PM, Sloane Bernstein wrote:
Hello,
I believe that the description of the WEXITSTATUS() macro from the
wait(2) manpage <http://man7.org/linux/man-pages/man2/wait.2.html> is
either incorrect or very unclear:
WEXITSTATUS(wstatus)
returns the exit status of the child. This consists of the
least significant 8 bits of the wstatus argument that the
child specified in a call to exit(3) or _exit(2) or as the
argument for a return statement in main(). This macro should
be employed only if WIFEXITED returned true.
The system's headers (it's a CentOS 6.8 system I pulled these from,
IIRC) themselves define the macro as:
# define WEXITSTATUS(status) __WEXITSTATUS (__WAIT_INT (status))
from sys/wait.h and
#define __WEXITSTATUS(status) (((status) & 0xff00) >> 8)
but a simplistic reading of the manpage entry seems to imply that the
latter definition should be:
#define __WEXITSTATUS(status) ((status) & 0xff)
It isn't, of course. When the manpage refers to "the wstatus
argument", it is too easy to associate it to the argument named in
the declaration of the macro just above, rather than to the single
argument of exit(3) or _exit(2) (which in both
<http://man7.org/linux/man-pages/man3/exit.3.html> and
<http://man7.org/linux/man-pages/man2/_exit.2.html> is actually
called "status", not "wstatus").
Because both exit(3) and _exit(2) only take a single argument, I
would suggest striking "wstatus" from the text of the explanation of
WEXITSTATUS(), since it is not ambiguous which argument of those
functions is being referred to.
So, the "status" that you point is indeed a typo. I accidentally
injected that typo during a recent global edit. It should read "status"
and I've now fixed the page to reflect that, so the text now reads:
WEXITSTATUS(wstatus)
returns the exit status of the child. This consists of the
least significant 8 bits of the status argument that the
child specified in a call to exit(3) or _exit(2) or as the
argument for a return statement in main(). This macro
should be employed only if WIFEXITED returned true.
Thanks for the report!
Cheers,
Michael
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
--
To unsubscribe from this list: send the line "unsubscribe linux-man" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
