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14249 pseudo-terminal nomenclature should reflect POSIX
Change-Id: Ib4a3cef899ff4c71b09cb0dc6878863c5e8357bc
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--- old/usr/src/man/man7d/ptm.7d.man.txt
+++ new/usr/src/man/man7d/ptm.7d.man.txt
1 1 PTM(7D) Devices PTM(7D)
2 2
3 3 NAME
4 - ptm - STREAMS pseudo-tty master driver
4 + ptm, pts - STREAMS pseudo-terminal manager and subsidiary drivers
5 5
6 +SYNOPSIS
7 + /dev/ptmx
8 +
9 + /dev/pts/*
10 +
6 11 DESCRIPTION
7 - The pseudo-tty subsystem simulates a terminal connection, where the
8 - master side represents the terminal and the slave represents the user
9 - process's special device end point. In order to use the pseudo-tty
10 - subsystem, a node for the master side driver /dev/ptmx and N number of
11 - nodes for the slave driver must be installed. See pts(7D). The master
12 - device is set up as a cloned device where its major device number is
13 - the major for the clone device and its minor device number is the major
14 - for the ptm driver. There are no nodes in the file system for master
15 - devices. The master pseudo driver is opened using the open(2) system
16 - call with /dev/ptmx as the device parameter. The clone open finds the
17 - next available minor device for the ptm major device.
12 + The pseudo-terminal subsystem simulates a terminal connection, where the
13 + manager side represents the terminal and the subsidiary represents the
14 + user process's special device end point. The manager device is set up as
15 + a cloned device where its major device number is the major for the clone
16 + device and its minor device number is the major for the ptm driver; see
17 + CLONE_DEV in ddi_create_minor_node(9F).
18 18
19 + There are no nodes in the file system for manager devices. The manager
20 + pseudo driver is opened using the open(2) system call with /dev/ptmx as
21 + the device parameter. The clone open finds the next available minor
22 + device for the ptm major device.
19 23
20 - A master device is available only if it and its corresponding slave
21 - device are not already open. When the master device is opened, the
22 - corresponding slave device is automatically locked out. Only one open
23 - is allowed on a master device. Multiple opens are allowed on the slave
24 - device. After both the master and slave have been opened, the user has
25 - two file descriptors which are the end points of a full duplex
26 - connection composed of two streams which are automatically connected at
27 - the master and slave drivers. The user may then push modules onto
28 - either side of the stream pair.
24 + A manager device is only available if it and its corresponding subsidiary
25 + device are not already open. Only one open is allowed on a manager
26 + device. Multiple opens are allowed on the subsidiary device.
29 27
28 + When the manager device is opened, the corresponding subsidiary device is
29 + automatically locked out. No user may open the subsidiary device until
30 + its permissions are adjusted and the device is unlocked by calling the
31 + functions grantpt(3C) and unlockpt(3C). The user can then invoke the
32 + open(2) system call with the device name returned by the ptsname(3C)
33 + function.
30 34
31 - The master and slave drivers pass all messages to their adjacent
32 - queues. Only the M_FLUSH needs some processing. Because the read queue
33 - of one side is connected to the write queue of the other, the FLUSHR
34 - flag is changed to the FLUSHW flag and vice versa. When the master
35 - device is closed an M_HANGUP message is sent to the slave device which
36 - will render the device unusable. The process on the slave side gets the
37 - errno EIO when attempting to write on that stream but it will be able
38 - to read any data remaining on the stream head read queue. When all the
39 - data has been read, read() returns 0 indicating that the stream can no
40 - longer be used. On the last close of the slave device, a 0-length
41 - message is sent to the master device. When the application on the
42 - master side issues a read() or getmsg() and 0 is returned, the user of
43 - the master device decides whether to issue a close() that dismantles
44 - the pseudo-terminal subsystem. If the master device is not closed, the
45 - pseudo-tty subsystem will be available to another user to open the
46 - slave device.
35 + After both the manager and subsidiary have been opened, the user has two
36 + file descriptors which are the end points of a full duplex connection
37 + composed of two streams which are automatically connected at the manager
38 + and subsidiary drivers. The user may then push modules onto either side
39 + of the stream pair. Unless compiled in XPG4v2 mode (see XPG4v2 MODE),
40 + the consumer needs to push the ptem(7M) and ldterm(7M) modules onto the
41 + subsidiary device to get terminal semantics.
47 42
43 + The manager and subsidiary drivers pass all messages to their adjacent
44 + queues. Only the M_FLUSH needs some processing. Because the read queue
45 + of one side is connected to the write queue of the other, the FLUSHR flag
46 + is changed to the FLUSHW flag and vice versa.
48 47
49 - If O_NONBLOCK or O_NDELAY is set, read on the master side returns -1
50 - with errno set to EAGAIN if no data is available, and write returns -1
51 - with errno set to EAGAIN if there is internal flow control.
48 + When the manager device is closed, an M_HANGUP message is sent to the
49 + subsidiary device which will render the device unusable. The process on
50 + the subsidiary side gets an EIO error when attempting to write on that
51 + stream, but it will be able to read any data remaining on the stream head
52 + read queue. When all the data has been read, read(2) returns 0
53 + indicating that the stream can no longer be used.
52 54
55 + On the last close of the subsidiary device, a 0-length message is sent to
56 + the manager device. When the application on the manager side issues a
57 + read(2) or getmsg(2) and 0 is returned, the user of the manager device
58 + decides whether to issue a close(2) that dismantles the entire pseudo-
59 + terminal. If the manager device is not closed, the pseudo-terminal will
60 + be available to another user to open the subsidiary device.
61 +
62 + Since 0-length messages are used to indicate that the process on the
63 + subsidiary side has closed, and should be interpreted that way by the
64 + process on the manager side, applications on the subsidiary side should
65 + not write 0-length messages. Unless the application is compiled in
66 + XPG4v2 mode (see XPG4v2 MODE), then any 0-length messages written to the
67 + subsidiary device will be discarded by the ptem(7M) module.
68 +
69 + If O_NONBLOCK or O_NDELAY is set on the manager side:
70 +
71 + o Read on the manager side returns -1 with errno set to EAGAIN if no
72 + data is available
73 +
74 + o Write returns -1 with errno set to EAGAIN if there is internal flow
75 + control
76 +
77 + Standard STREAMS system calls can access pseudo-terminal devices. The
78 + subsidiary devices support the O_NDELAY and O_NONBLOCK flags.
79 +
80 +XPG4v2 MODE
81 + XPG4v2 requires that subsidiary pseudo-terminal devices provide the
82 + process with an interface that is identical to the terminal interface,
83 + without needing to explicitly push any modules to achieve this. It also
84 + requires that 0-length messages written on the subsidiary device will be
85 + propagated to the manager device.
86 +
87 + Experience has shown that most software does not expect subsidiary
88 + pseudo-terminal devices to operate in this manner. This XPG4v2-compliant
89 + behaviour is only enabled in XPG4v2/SUS (see standards(5)) mode.
90 +
53 91 IOCTLS
54 - The master driver supports the ISPTM and UNLKPT ioctls that are used by
55 - the functions grantpt(3C), unlockpt(3C) and ptsname(3C). The ioctl
56 - ISPTM determines whether the file descriptor is that of an open master
57 - device. On success, it returns the 0. The ioctl UNLKPT unlocks the
58 - master and slave devices. It returns 0 on success. On failure, the
59 - errno is set to EINVAL indicating that the master device is not open.
92 + The manager driver provides several ioctls to support the grantpt(3C),
93 + unlockpt(3C), and ptsname(3C) functions:
60 94
95 + ISPTM Determines whether the file descriptor is that of an open manager
96 + device. On success, it returns the value 0.
97 +
98 + UNLKPT Unlocks the manager and subsidiary devices. It returns 0 on
99 + success. On failure, errno is set to EINVAL indicating that the
100 + manager device is not open.
101 +
61 102 FILES
62 - /dev/ptmx
63 - master clone device
103 + /dev/ptmx Pseudo-terminal manager clone device.
64 104
105 + /dev/pts/N Pseudo-terminal subsidiary devices,
106 + where N is a non-negative integer.
107 + Located via calls to ptsname(3C).
65 108
66 - /dev/pts/M
67 - slave devices (M = 0 -> N-1)
109 +EXAMPLES
110 + Example 1 Opening the manager and subsidiary device for a pseudo-
111 + terminal.
68 112
113 + #include <stdlib.h>
114 + #include <sys/types.h>
115 + #include <sys/stat.h>
116 + #include <unistd.h>
117 + #include <stropts.h>
118 + #include <fcntl.h>
119 + #include <err.h>
120 + ...
121 + int fdm, fds;
122 + char *subsidiaryname;
123 + ...
124 + /*
125 + * NOTE: Portable applications should use posix_openpt(3C) here:
126 + */
127 + if ((fdm = open("/dev/ptmx", O_RDWR | O_NOCTTY)) < 0) {
128 + err(1, "open manager");
129 + }
130 + if (grantpt(fdm) != 0 || unlockpt(fdm) != 0 ||
131 + (subsidiaryname = ptsname(fdm)) == NULL) {
132 + close(fdm);
133 + err(1, "locate subsidiary");
134 + }
135 + if ((fds = open(subsidiaryname, O_RDWR | O_NOCTTY)) < 0) {
136 + close(fdm);
137 + err(1, "open subsidiary");
138 + }
139 + if (ioctl(fds, I_PUSH, "ptem") != 0 ||
140 + ioctl(fds, I_PUSH, "ldterm") != 0) {
141 + close(fds);
142 + close(fdm);
143 + err(1, "push modules");
144 + }
69 145
70 146 SEE ALSO
71 - grantpt(3C), ptsname(3C), unlockpt(3C), pckt(7M), pts(7D)
147 + close(2), getmsg(2), open(2), read(2), grantpt(3C), posix_openpt(3C),
148 + ptsname(3C), unlockpt(3C), standards(5), ldterm(7M), pckt(7M), ptem(7M),
149 + ddi_create_minor_node(9F)
72 150
73 -
74 - STREAMS Programming Guide
75 -
76 - February 5, 1997 PTM(7D)
151 +illumos February 5, 2022 illumos
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