TCFLOW(3) Library Functions Manual TCFLOW(3)

tcflow — suspend or restart the transmission or reception of data

#include <termios.h>

int tcflow(int fildes, int action);

The tcflow() function suspends 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 is suspended.
  • If action is TCOON, suspended output is restarted.
  • If action is TCIOFF, the system transmits a STOP character, which is intended to cause the terminal device to stop transmitting data to the system.
  • If action is TCION, the system transmits 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 associated with its controlling terminal, will cause the process group to be sent a SIGTTOU signal. If the calling process is blocking or ignoring SIGTTOU signals, the process is allowed to perform the operation, and no signal is sent.

Upon successful completion, 0 is returned. Otherwise, -1 is returned and errno is set to indicate the error.

The tcflow() function will 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.

None.

None.

In the ISO POSIX-1 standard, the possibility of an [EIO] error occurring is described in XBD specification, , but it is not mentioned in the tcflow() interface definition. It has become clear that this omission was unintended, so it is likely that the [EIO] error will be re-classified as a "will fail" in a future issue of the POSIX standard.

tcsendbreak(3) , <termios.h> , <unistd.h> , the XBD specification, .

Derived from the POSIX.1-1988 standard.

February 1997 posix.fail