You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
44 lines
1.6 KiB
Groff
44 lines
1.6 KiB
Groff
.TH io_nonblock 3
|
|
.SH NAME
|
|
io_nonblock \- switch to non-blocking I/O
|
|
.SH SYNTAX
|
|
.B #include <io.h>
|
|
|
|
void \fBio_nonblock\fP(int64 fd);
|
|
.SH DESCRIPTION
|
|
io_nonblock puts UNIX descriptor fd into ``non-blocking mode.'' Calling
|
|
io_nonblock(\fIfd\fR) before io_fd(\fIfd\fR) makes io_tryread and
|
|
io_trywrite faster and more efficient.
|
|
|
|
Actually, current UNIX kernels do not support non-blocking descriptors; they
|
|
support non-blocking open files. Furthermore, many programs will break if they
|
|
encounter non-blocking mode. This means that you must not use io_nonblock for a
|
|
descriptor inherited from another program.
|
|
|
|
io_nonblock has no return value; it always succeeds. If d is not the number of
|
|
a UNIX descriptor, io_nonblock has no effect.
|
|
|
|
If io_fd is given a descriptor in blocking mode, io_tryread and io_trywrite go
|
|
through the following contortions to avoid blocking:
|
|
|
|
.RS 0
|
|
.nr step 1 1
|
|
.IP \n[step] 3
|
|
Stop if poll says that the descriptor is not ready. Otherwise there's a good
|
|
chance, but not a guarantee: even if poll says the descriptor is ready, the
|
|
descriptor might not be ready a moment later. (Furthermore, poll can fail on
|
|
some systems.)
|
|
.IP \n+[step]
|
|
Catch SIGALRM. SIGALRM must not be blocked, and must not be used elsewhere in
|
|
the program.
|
|
.IP \n+[step]
|
|
Set an interval timer so that any blocking call will be interrupted by SIGALRM
|
|
within 10 milliseconds. (Current UNIX kernels do not allow any shorter
|
|
interval.) Of course, this may still mean a 10-millisecond delay.
|
|
.RE
|
|
|
|
If io_fd is given a descriptor in non-blocking mode (or a descriptor for a
|
|
regular disk file), io_tryread and io_trywrite avoid these contortions.
|
|
.SH "SEE ALSO"
|
|
io_wait(3), io_canwrite(3)
|