debian man page for io_tryread

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)