NAME

       io_tryread - read from a descriptor without blocking

SYNTAX

       #include <libowfat/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_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.

       •  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.

       •  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.

       •  io_tryread returns -3, setting errno to something other than EAGAIN: No bytes were read,  because  the
          read  attempt  encountered  a  persistent  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)