The tcdrain() function waits until all output written to the object referred to by fildes is transmitted. The fildes argument is an open file descriptor associated with a terminal.

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, will cause the process group to be sent a SIGTTOU signal. If the calling process is blocking or ignoring SIGTTOU signals, the process is allowed to perform the operation, and no signal is sent.

Upon successful completion, 0 is returned. Otherwise, -1 is returned and errno is set to indicate the error.

The tcdrain() function will fail if:

EBADF

The fildes argument is not a valid file descriptor.

EINTR

A signal interrupted tcdrain().

ENOTTY

The file associated with fildes is not a terminal.

The tcdrain() function may fail if:

EIO

The process group of the writing process is orphaned, and the writing process is not ignoring or blocking SIGTTOU.

See attributes(5) for descriptions of the following attributes:

tcflush(3C), attributes(5), termio(7I)