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io_nonblock(3) [debian man page]

io_nonblock(3)						     Library Functions Manual						    io_nonblock(3)

NAME
io_nonblock - switch to non-blocking I/O SYNTAX
#include <io.h> void io_nonblock(int64 fd); DESCRIPTION
io_nonblock puts UNIX descriptor fd into ``non-blocking mode.'' Calling io_nonblock(fd) before io_fd(fd) 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 pro- gram. 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: 1 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 descrip- tor is ready, the descriptor might not be ready a moment later. (Furthermore, poll can fail on some systems.) 2 Catch SIGALRM. SIGALRM must not be blocked, and must not be used elsewhere in the program. 3 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. 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 con- tortions. SEE ALSO
io_wait(3), io_canwrite(3) io_nonblock(3)

Check Out this Related Man Page

io_tryread(3)						     Library Functions Manual						     io_tryread(3)

NAME
io_tryread - read from a descriptor without blocking SYNTAX
#include <io.h> int io_tryread(int64 fd,char* buf,int64 len); DESCRIPTION
io_tryread tries to read len bytes of data from descriptor fd into buf[0], buf[1], ..., buf[len-1]. (The effects are undefined if len is 0 or smaller.) There are several possible results: o o_tryread returns an integer between 1 and len: This number of bytes was available for immediate reading; the bytes were read into the beginning of buf. Note that this number can be, and often is, smaller than len; you must not assume that io_tryread always succeeds in reading exactly len bytes. o io_tryread returns 0: No bytes were read, because the descriptor is at end of file. For example, this descriptor has reached the end of a disk file, or is reading an empty pipe that has been closed by all writers. o io_tryread returns -1, setting errno to EAGAIN: No bytes were read, because the descriptor is not ready. For example, the descriptor is reading an empty pipe that could still be written to. o io_tryread returns -3, setting errno to something other than EAGAIN: No bytes were read, because the read attempt encountered a persis- tent error, such as a serious disk failure (EIO), an unreachable network (ENETUNREACH), or an invalid descriptor number (EBADF). io_tryread does not pause waiting for a descriptor that is not ready. If you want to pause, use io_waitread or io_wait. You can make io_tryread faster and more efficient by making the socket non-blocking with io_nonblock(). SEE ALSO
io_nonblock(3), io_waitread(3), io_tryreadtimeout(3) io_tryread(3)
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