tcflow (BPX1TFW, BPX4TFW) — Suspend or resume data flow on a terminal

Function

The tcflow callable service suspends or resumes data flow on a terminal.

Requirements

Operation	Environment
Authorization:	Supervisor or problem state, any PSW key
Dispatchable unit mode:	Task
Cross memory mode:	PASN = HASN
AMODE (BPX1TFW):	31-bit
AMODE (BPX4TFW):	64-bit
ASC mode:	Primary mode
Interrupt status:	Enabled for interrupts
Locks:	Unlocked
Control parameters:	All parameters must be addressable by the caller and in the primary address space.

Format

CALL BPX1TFW,(File_descriptor,
              Action,
              Return_value,
              Return_code,
              Reason_code)

AMODE 64 callers use BPX4TFW with the same parameters.

Parameters

File_descriptor

Supplied parameter

Type:: Integer
Length:: Fullword

The name of a fullword that contains the file descriptor for the terminal device.

Action

Supplied parameter

Type:: Integer
Length:: Fullword

The name of a fullword that contains an indicator of the action that is to be taken. The possible constants are mapped in the BPXYTIOS macro (see BPXYTIOS — Map the termios structure).

Constant	Description
TCIOFF	Send a STOP character to the terminal to stop the terminal from sending any further input.
TCION	Send a START character to the terminal to start the terminal sending input.
TCOOFF	Suspend output to the terminal.
TCOON	Resume output to the terminal.

Return_value

Returned parameter

Type:: Integer
Length:: Fullword

The name of a fullword in which the tcflow service returns 0 if the request is successful, or -1 if it is not successful.

Return_code

Returned parameter

Type:: Integer
Length:: Fullword

The name of a fullword in which the tcflow service stores the return code. The tcflow service returns Return_code only if Return_value is -1. See z/OS UNIX System Services Messages and Codes for a complete list of possible return code values. The tcflow service can return one of the following values in the Return_code parameter:

Return_code	Explanation
EBADF	File_descriptor does not describe a valid open file.
EINTR	A signal interrupted the call.
EINVAL	The Action parameter does not contain one of the expected values.
EIO	The process group of the process that is issuing the function is an orphaned, background process group, and the process that is issuing the function is not ignoring or blocking SIGTTOU.
ENOTTY	File_descriptor is not associated with a terminal.

Reason_code

Returned parameter

Type:: Integer
Length:: Fullword

The name of a fullword in which the tcflow service stores the reason code. The tcflow service returns Reason_code only if Return_value is -1. Reason_code further qualifies the Return_code value. For the reason codes, see z/OS UNIX System Services Messages and Codes.

Usage notes

The following table defines the processing of the SIGTTOU signal when the tcflow service is called from a background process against a controlling terminal:

SIGTTOU processing	Expected behavior
Default or signal handler	The SIGTTOU signal is generated. The function is not performed. Return_value is set to -`1`, and Return_code is set to EINTR.
Ignored or blocked	The SIGTTOU signal is not sent. The function continues normally.

tcflow (BPX1TFW, BPX4TFW) — Suspend or resume data flow on a terminal

Function

Requirements

Format

Parameters

Usage notes

Related services

Characteristics and restrictions

Examples