Open System Services Library Calls Reference Manual (G06.29+, H06.08+, J06.03+)

OSS Library Calls (t - v) tcflow(3)
NAME
tcflow - Performs flow control functions
LIBRARY
G-series native OSS processes: system library
H-series and J-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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