Method _Stdio.Fd()->read_oob()

Method read_oob

string read_oob()
string read_oob(int len)
string read_oob(int len, bool not_all)

Description

Attempts to read len bytes of out-of-band data from the stream, and returns it as a string. Less than len bytes can be returned if:

  • the stream has been closed from the other end, or

  • nonblocking mode is used, or

  • not_all is set, or

  • not_all isn't set and an error occurred (see below).

If not_all is nonzero, read_oob() only returns as many bytes of out-of-band data as are currently available.

If something goes wrong and not_all is set, zero is returned. If something goes wrong and not_all is zero or left out, then either zero or a string shorter than len is returned. If the problem persists then a later call to read_oob() fails and returns zero, however.

If everything went fine, a call to errno() directly afterwards returns zero. That includes an end due to remote close.

If no arguments are given, read_oob() reads to the end of the stream.

Note

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.

Note

It's not necessary to set not_all to avoid blocking reading when nonblocking mode is used.

Note

When at the end of a file or stream, repeated calls to read() returns the empty string since it's not considered an error. The empty string is never returned in other cases, unless nonblocking mode is used or len is zero.

See also

read(), write_oob()