Open System Services Library Calls Reference Manual (G06.27+, H06.04+)

OSS Library Calls (t - v) tc
flow(3)
NAME
tcflow - Performs flow control functions
LIBRARY
G-series native OSS processes: system library
H-series OSS processes: implicit libraries
SYNOPSIS
#include <termios.h>
int tcflow(
int filedes,
int action);
PARAMETERS
filedes Specifies an open file descriptor.
action Specifies one of the following actions:
TCIOFF Transmits a Stop character, which is intended to cause the termi-
nal device to stop transmitting data to the system if the IXOFF
flag is set.
TCION Transmits a Start character, which is intended to cause the termi-
nal device to start transmitting data to the system if the IXOFF
flag is set.
TCOOFF Suspends output.
TCOON Restarts suspended output.
DESCRIPTION
The tcflow() function suspends transmission or reception of data on the object referred to by the
filedes parameter, depending on the value of the action parameter.
An attempt to use the tcflow() function from a process that is a member of a background process
group on a filedes associated with its controlling terminal causes the process group to be sent a
SIGTTOU signal. If the calling process is blocking or ignoring the SIGTTOU signal, the pro-
cess is allowed to perform the operation and no signal is sent.
RETURN VALUES
Upon successful completion, the value 0 (zero) is returned. Otherwise, the value -1 is returned
and errno is set to indicate the error.
ERRORS
If any of the following conditions occurs, the tcflow() function sets errno to the corresponding
value:
[EBADF] The filedes parameter does not specify a valid file descriptor.
[EINVAL] The action parameter is not a supported value.
[EIO] One of the following conditions exists:
• The process group of the caller is orphaned and the caller is not ignoring
or blocking the SIGTTOU signal.
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