unlockpt (BPX1UPT, BPX4UPT) — Unlock a pseudoterminal master/slave pair
Function
The unlockpt callable service unlocks the slave pseudoterminal device that is associated with the master to which the file descriptor refers.
Note: Because access to pseudoterminals
is granted by changing ownership during the first slave open, and
that caller must have the same UID as the master opener, neither the
grantpt nor the unlockpt services are functionally required. They
are provided in order to be compatible with XPG4, and for ported programs
that may use them.
Requirements
Operation | Environment |
---|---|
Authorization: | Supervisor or problem state, any PSW key |
Dispatchable unit mode: | Task |
Cross memory mode: | PASN = HASN |
AMODE (BPX1UPT): | 31-bit |
AMODE (BPX4UPT): | 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
The syntax format is as
follows:
CALL BPX1UPT,(File_descriptor,
Return_value,
Return_code,
Reason_code)
AMODE 64 callers use BPX4UPT 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.
- Return_value
- Returned parameter
- Type:
- Integer
- Length:
- Fullword
The name of a fullword in which the unlockpt 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 unlockpt service stores the return code. The unlockpt service returns Return_code only if Return_value is-1
. For a list of return code values, see Return codes (errnos) in z/OS UNIX System Services Messages and Codes. The unlockpt service can return one of the following values in the Return_code parameter:Return_code Explanation EACCES Either a grantpt has not yet been issued, or an unlockpt has already been issued. An unlockpt must be issued after a grantpt, and can only be issued once. EBADF The File_descriptor parameter does not specify a file descriptor that is open for writing. EINVAL The file descriptor is not associated with a master pseudoterminal device. - Reason_code
- Returned parameter
- Type:
- Integer
- Length:
- Fullword
The name of a fullword in which the unlockpt service stores the reason code. The unlockpt service returns Reason_code only if Return_value is
-1
. Reason_code further qualifies the Return_code value.For a list of reason codes, see Reason codes in z/OS UNIX System Services Messages and Codes.
Characteristics and restrictions
There are no restrictions on the use of the unlockpt service.