Login or Register to Ask a Question and Join Our Community

Linux and UNIX Man Pages

Linux & Unix Commands - Search Man Pages

io_canwrite(3) [debian man page]

io_canwrite(3)						     Library Functions Manual						    io_canwrite(3)

NAME

       io_canwrite - return a file descriptor that can be written to

SYNTAX

       #include <io.h>

       int64 io_canwrite();

DESCRIPTION

       io_canwrite  returns the next file descriptor that can be written to.  You have to have used io_wantwrite() 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 writable by the operating system.

       Please note that there is no guarantee that you can still write data without  blocking  to  that  descriptor,  just  that  you  could  when
       io_wait() or io_waituntil() were called.  Another process could have written something before you.  Look at the result from io_trywrite().

       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 only use io_trywrite(3), io_sendfile(3) or iob_send(3) to write to the file, not plain write(2).  If you use	write(2)  and  get
       EAGAIN, call io_eagain(3).

SEE ALSO

       io_wait(3), io_canwrite(3)

																    io_canwrite(3)

Check Out this Related Man Page

iob_send(3)						     Library Functions Manual						       iob_send(3)

NAME

       iob_send - send I/O batch

SYNTAX

       #include <iob.h>

       int64 iob_send(int64 s,io_batch* b);

DESCRIPTION

       iob_send sends the (rest of) b over the socket s.

       iob_send  returns  the number of bytes written, 0 if there were no more bytes to be written in the batch, -1 for EAGAIN, or -3 for a perma-
       nent error (for example "connection reset by peer").

       The normal usage pattern is using io_wait to know when a descriptor is writable, and then calling iob_send until it returns 0, -1 or -3.

       If it returns 0, terminate the loop (everything was written OK).  If it returns -1, call io_wait again.	If it returned -3, signal an error
       and close the socket.

       The benefit of the I/O batch API is that it exploits platform specific APIs like FreeBSD's sendfile.  The file contents will always be sent
       in a way that allows the operating systems to perform zero copy TCP, and the buffers will always be sent using as few syscalls as  possible
       and avoiding unnecessary copying (using writev).

SEE ALSO

       iob_reset(3), iob_send(3), iob_addbuf(3), iob_adds_free(3), iob_addfile(3), iob_prefetch(3)

																       iob_send(3)
Man Page