tcflush - Man Page

flush non-transmitted output data, non-read input data, or both


This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.


#include <termios.h>

int tcflush(int fildes, int queue_selector);


Upon successful completion, tcflush() shall discard data written to the object referred to by fildes (an open file descriptor associated with a terminal) but not transmitted, or data received but not read, depending on the value of queue_selector:


If queue_selector is TCIFLUSH, it shall flush data received but not read.


If queue_selector is TCOFLUSH, it shall flush data written but not transmitted.


If queue_selector is TCIOFLUSH, it shall flush both data received but not read and data written but not transmitted.

Attempts to use tcflush() 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 tcflush() function shall fail if:


The fildes argument is not a valid file descriptor.


The queue_selector argument is not a supported value.


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


The file associated with fildes is not a terminal.

The following sections are informative.



Application Usage




Future Directions


See Also


The Base Definitions volume of POSIX.1-2017, Chapter 11, General Terminal Interface, <termios.h>

Referenced By

tcdrain(3p), termios.h(0p).

2017 IEEE/The Open Group POSIX Programmer's Manual