Method _Stdio.Fd()->write_oob()

Method write_oob

int write_oob(string data)
int write_oob(string format, mixed ... extras)


Write out-of-band data to a stream.

Writes out-of-band data to a stream and returns how many bytes that were actually written. It can be less than the size of the given data if some data was written successfully and then something went wrong.

-1 is returned if something went wrong and no bytes were written. If only some data was written due to an error and that error persists, then a later call to write_oob() fails and returns -1.

If everything went fine, a call to errno() directly afterwards returns zero.

If more than one argument is given, sprintf() is used to format them.


It is not guaranteed that all out-of-band data sent from the other end is received. Most streams only allow for a single byte of out-of-band data at a time. Some streams sends the rest of the data as ordinary data.

See also

read_oob(), write()