The Open Group Base Specifications Issue 8
IEEE Std 1003.1-2024
Copyright © 2001-2024 The IEEE and The Open Group

NAME

tcflow — suspend or restart the transmission or reception of data

SYNOPSIS

#include <termios.h>

int tcflow(int
fildes, int action);

DESCRIPTION

The tcflow() function shall suspend or restart transmission or reception of data on the object referred to by fildes, depending on the value of action. The fildes argument is an open file descriptor associated with a terminal.

The default on the opening of a terminal file is that neither its input nor its output are suspended.

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

[EBADF]
The fildes argument is not a valid file descriptor.
[EINVAL]
The action 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

tcsendbreak

XBD 11. General Terminal Interface , <termios.h>

CHANGE HISTORY

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

Issue 6

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

Issue 7

SD5-XSH-ERN-190 is applied, clarifying in the DESCRIPTION the transmission of START and STOP characters.

POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0642 [79], XSH/TC1-2008/0643 [79], and XSH/TC1-2008/0644 [79] are applied.

End of informative text.

 

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