The tcdrain() function shall block until all output written
to the object referred to by fildes is transmitted.
The fildes argument is an open file descriptor associated with
Any attempts to use tcdrain() from a process which is a member
of a background process group on a fildes
associated with its controlling terminal, shall cause the process
group to be sent a SIGTTOU signal. If the calling process is
blocking or ignoring SIGTTOU signals, the process shall be allowed
to perform the operation, and no signal is sent.
Upon successful completion, 0 shall be returned. Otherwise, -1 shall
be returned and errno set to indicate the error.
The tcdrain() function shall fail if:
The fildes argument is not a valid file descriptor.
A signal interrupted tcdrain().
The file associated with fildes is not a terminal.
The tcdrain() function may fail if:
The process group of the writing process is orphaned, and the writing
process is not ignoring or blocking SIGTTOU.
The following sections are informative.
tcflush() , the Base Definitions volume of IEEE Std 1003.1-2001,
Chapter 11, General Terminal Interface, <termios.h>, <unistd.h>
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at