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)
Check Out this Related Man Page
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)
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