io_trywrite man page

io_trywrite — write to a descriptor without blocking


#include <io.h>

int io_trywrite(int64 fd,const char* buf,int64 len);


io_trywrite tries to write len bytes of data from buf[0], buf[1], ..., buf[len-1] to descriptor fd. (The effects are undefined if len is 0 or smaller.) There are several possible results:

io_trywrite 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_trywrite faster and more efficient by making the socket non-blocking with io_nonblock().

Once upon a time, many UNIX programs neglected to check the success of their writes. They would often encounter EPIPE, and would blithely continue writing, rather than exiting with an appropriate exit code. The UNIX kernel developers decided to send a SIGPIPE signal, which terminates the process by default, along with returning EPIPE. This papers over the problem without fixing it: the same programs ignore other errors such as EIO. One hopes that the programs have been fixed by now; kernels nevertheless continue to generate the SIGPIPE signal. The first time io_trywrite or io_waitwrite is called, it arranges for SIGPIPE to be ignored.  (Technically, for SIGPIPE to be caught by an empty signal handler, so this doesn't affect child processes.) Do not use SIGPIPE elsewhere in the program.

See Also

io_nonblock(3), io_waitread(3), io_trywritetimeout(3)

Referenced By

io_canwrite(3), io_trywritetimeout(3).