#include <termios.h>

int tcdrain(int fildes);


Partially implemented


IEEE Std 1003.1-2017


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

Return value#

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:

  • EBADF - The fildes argument is not a valid file descriptor.

  • EINTR - A signal interrupted tcdrain().

  • EIO - The process group of the writing process is orphaned, the calling thread is not blocking SIGTTOU, and the process is not ignoring SIGTTOU.

  • ENOTTY - The file associated with fildes is not a terminal.



Known bugs#


See Also#

  1. Standard library functions

  2. Table of Contents