debian man page for io_canread

io_canread(3)						     Library Functions Manual						     io_canread(3)

NAME
       io_canread - return a file descriptor that can be read from

SYNTAX
       #include <io.h>

       int64 io_canread();

DESCRIPTION
       io_canread returns the next file descriptor that can be read from.  You have to have used io_wantread() on the file descriptor earlier, and
       you have to have called io_wait() or io_waituntil().

       These functions then keep an internal data structure on which descriptors were reported readable by the operating system.

       Please note that there is no guarantee that there still is data that can be read from  the  descriptor,	just  that  there  was	data  when
       io_wait() or io_waituntil() were called.  Another process could have read the data before you.  Look at the result from io_tryread().

       If  there  are  no  more  descriptors  that  you  can  write to without blocking, io_canwrite will return -1.  In this case you should call
       io_wait() or io_waituntil() again.

       You should use io_tryread(3) to read from the descriptor, not plain read(2).  If you use read(2) and you get EAGAIN, call io_eagain(3).

SEE ALSO
       io_wait(3), io_canwrite(3), io_eagain(3)

																     io_canread(3)