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
|
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. |
Ignored or blocked | The SIGTTOU signal is not sent. |
Related services
Characteristics and restrictions
There are no restrictions on the use of the tcflow service.
Examples
For an example using this callable service, see BPX1TFW (tcflow) example.