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.

• If action is TCOOFF, output shall be suspended.

• If action is TCOON, suspended output shall be restarted.

• If action is TCIOFF, the system shall transmit a STOP character, which is intended to cause the terminal device to stop transmitting data to the system.

• If action is TCION, the system shall transmit a START character, which is intended to cause the terminal device to start transmitting data to the system.

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 process is blocking or 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.

[ENOTTY]

The file associated with fildes is not a terminal.

The tcflow() function may fail if:

[EIO]

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

EXAMPLES

None.

APPLICATION USAGE

None.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

tcsendbreak() , the Base Definitions volume of IEEE Std 1003.1-2001, Chapter 11, General Terminal Interface, <termios.h>, <unistd.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:

• The [EIO] error is added.