# tcflow

## PROLOG



           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.
    


## 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 and _fildes_ refers to a terminal device,
               the system shall transmit a STOP character, which is intended
               to cause the terminal device to stop transmitting data to the
               system. If _fildes_ is associated with a pseudo-terminal, the
               STOP character need not be transmitted.
    
            *  If _action_ is TCION and _fildes_ refers to a terminal device, the
               system shall transmit a START character, which is intended to
               cause the terminal device to start transmitting data to the
               system. If _fildes_ is associated with a pseudo-terminal, the
               START character need not be transmitted.
    
           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.
    


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