STREAMS Programming Guide

`grantpt`

grantpt(3C) changes the mode and the ownership of the slave device that is associated with the given master device. Given a file descriptor fd, grantpt(3C) first checks that the file descriptor is that of the master device. If so, it obtains the name of the associated slave device and sets the user ID to that of the user running the process and the group ID to TTY. The mode of the slave device is set to 0620.

If the process is already running as root, the permission of the slave can be changed directly without invoking this function. grantpt(3C) returns 0 on success and -1 on failure. It fails if one or more of the following occurs: fd is not an open file descriptor, fd is not associated with a master device, the corresponding slave could not be accessed, or a system call failed because no more processes could be created.

`unlockpt`

unlockpt(3C) clears a lock flag associated with a master/slave device pair. unlockpt(3C) returns 0 on success and -1 on failure. It fails if one or more of the following occurs: fd is not an open file descriptor or fd is not associated with a master device.

`ptsname`

ptsname(3C) returns the name of the slave device that is associated with the given master device. It first checks that the file descriptor is that of the master. If it is, it then determines the name of the corresponding slave device /dev/pts/M and returns a pointer to a string containing the null-terminated path name. The return value points to static data whose content is overwritten by each call. ptsname(3C) returns a non-NULL path name upon success and a NULL pointer upon failure. It fails if one or more of the following occurs: fd is not an open file descriptor or fd is not associated with the master device.

Pseudo-TTY Streams

Drivers and modules can make the stream head act as a terminal stream by sending an M_SETOPTS message with the SO_ISTTY flag set upstream. This state may be changed by sending an M_SETOPTS message with the SO_ISNTTY flag set upstream.

Controlling terminals are allocated with the open(2) interface. The device must tell the stream head that it is acting as a terminal.

The TOSTOP flag is set on reception of an M_SETOPTS message with the SO_TOSTOP flag set in the so_flags field. It is cleared on reception of an M_SETOPTS message with the SO_TONSTOP flag set.

Stream head processing is isolated from modules and drivers by using several message types, such as M_ERROR, M_HANGUP and M_SETOPS, which only affect the stream in which they are sent.


C. STREAMS-Based Terminal Subsystem STREAMS-based Pseudo-Terminal Subsystem Pseudo-TTY Drivers: `ptm` and `pts`


	`grantpt` `grantpt`(3C) changes the mode and the ownership of the slave device that is associated with the given master device. Given a file descriptor `fd`, `grantpt`(3C) first checks that the file descriptor is that of the master device. If so, it obtains the name of the associated slave device and sets the user ID to that of the user running the process and the group ID to TTY. The mode of the slave device is set to 0620. If the process is already running as root, the permission of the slave can be changed directly without invoking this function. `grantpt`(3C) returns 0 on success and -1 on failure. It fails if one or more of the following occurs: `fd` is not an open file descriptor, `fd` is not associated with a master device, the corresponding slave could not be accessed, or a system call failed because no more processes could be created. `unlockpt` `unlockpt`(3C) clears a lock flag associated with a master/slave device pair. `unlockpt`(3C) returns 0 on success and -1 on failure. It fails if one or more of the following occurs: `fd` is not an open file descriptor or `fd` is not associated with a master device. `ptsname` `ptsname`(3C) returns the name of the slave device that is associated with the given master device. It first checks that the file descriptor is that of the master. If it is, it then determines the name of the corresponding slave device `/dev/pts/`M and returns a pointer to a string containing the null-terminated path name. The return value points to static data whose content is overwritten by each call. `ptsname`(3C) returns a non-NULL path name upon success and a NULL pointer upon failure. It fails if one or more of the following occurs: `fd` is not an open file descriptor or `fd` is not associated with the master device. Pseudo-TTY Streams Drivers and modules can make the stream head act as a terminal stream by sending an `M_SETOPTS` message with the `SO_ISTTY` flag set upstream. This state may be changed by sending an `M_SETOPTS` message with the `SO_ISNTTY` flag set upstream. Controlling terminals are allocated with the `open`(2) interface. The device must tell the stream head that it is acting as a terminal. The `TOSTOP` flag is set on reception of an `M_SETOPTS` message with the `SO_TOSTOP` flag set in the `so_flags` field. It is cleared on reception of an `M_SETOPTS` message with the `SO_TONSTOP` flag set. Stream head processing is isolated from modules and drivers by using several message types, such as `M_ERROR`, `M_HANGUP` and `M_SETOPS`, which only affect the stream in which they are sent.