The Open Group Base Specifications Issue 7
IEEE Std 1003.1-2008, 2016 Edition
Copyright © 2001-2016 The IEEE and The Open Group

#### NAME

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

#### SYNOPSIS

> ``#include <termios.h>
> int tcflush(int` fildes`, int` queue_selector`);
> ``

#### DESCRIPTION

> 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.

#### ERRORS

> The tcflush() function shall fail if:

> [EBADF]
>   The fildes argument is not a valid file descriptor.
> [EINVAL]
>   The queue_selector argument is not a supported value.
> [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.

The following sections are informative.

#### EXAMPLES

> None.

#### APPLICATION USAGE

> None.

#### RATIONALE

> None.

#### FUTURE DIRECTIONS

> None.

#### SEE ALSO

> tcdrain

> XBD General Terminal Interface, <termios.h>

#### CHANGE HISTORY

> First released in Issue 3. Included for alignment with the POSIX.1-1988 standard.

#### Issue 6

> The Open Group Corrigendum U035/1 is applied. In the ERRORS and APPLICATION USAGE sections, references to tcflow() are replaced with tcflush().

> The following new requirements on POSIX implementations derive from alignment with the Single UNIX Specification:

> - In the DESCRIPTION, the final paragraph is no longer conditional on _POSIX_JOB_CONTROL. This is a FIPS requirement.

> - The [EIO] error is added.

#### Issue 7

> POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0645 [79], XSH/TC1-2008/0646 [79], and XSH/TC1-2008/0647 [79] are applied.

End of informative text.

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