Eric Blake [ebl...@redhat.com] wrote:
| On 11/22/2010 03:16 PM, Chet Ramey wrote:
| >> include/filecntl.h in bash-4.1 has following:
| >>
| >> #define SET_CLOSE_ON_EXEC(fd) (fcntl ((fd), F_SETFD, FD_CLOEXEC))
| >>
| >> Is that really the correct/intended usage of F_SETFD ?
| >
| > F_SETFD Set the close-on-exec flag associated with fildes to
| > the low order bit of arg (0 or 1 as above).
Is that the POSIX definition ? Following man page does not limit F_SETFD to
FD_CLOEXEC:
http://www.kernel.org/doc/man-pages/online/pages/man2/fcntl.2.html
F_SETFD (long)
Set the file descriptor flags to the value specified by arg.
| >
| >> If kernel ever adds a new flag to the fd, this would end up clearing the
| >> other new flag right ?
| >>
| >> Shouldn't bash use F_GETFD to get the current flags and set/clear just
| >> the FD_CLOEXEC bit ?
| >
| > I suppose it would matter if there are systems that have more than one
| > flag value.
|
| In practice, there aren't any such systems; but POSIX warns that current
| practice is no indicator of future systems, and that read-modify-write
| is the only way to use F_SETFD.
Yes, that seems to make more sense.
Sukadev
