int tcflow(int fildes, int action);
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.
Upon successful completion, 0 shall be returned. Otherwise, -1 shall be returned and errno set to indicate the error.
The tcflow() function shall fail if:
- The fildes argument is not a valid file descriptor.
- The action argument is not a supported value.
The file associated with fildes is not a terminal.
The tcflow() function may fail if:
The process group of the writing process is orphaned, and the writing
process is not ignoring or blocking SIGTTOU.
The following sections are informative.
COPYRIGHTPortions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .