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io_tryread(3)         DragonFly 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
          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)