#include <termios.h>
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:
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
| Interface Stability | Standard |
| MT-Level | MT-Safe, and Async-Signal-Safe |
tcflush(3C), attributes(5), standards(5), termio(7I)