]>
Commit | Line | Data |
---|---|---|
fea681da MK |
1 | .\" Copyright (C) 2002 Andries Brouwer <aeb@cwi.nl> |
2 | .\" | |
3 | .\" Permission is granted to make and distribute verbatim copies of this | |
4 | .\" manual provided the copyright notice and this permission notice are | |
5 | .\" preserved on all copies. | |
6 | .\" | |
7 | .\" Permission is granted to copy and distribute modified versions of this | |
8 | .\" manual under the conditions for verbatim copying, provided that the | |
9 | .\" entire resulting derived work is distributed under the terms of a | |
10 | .\" permission notice identical to this one. | |
c13182ef | 11 | .\" |
fea681da MK |
12 | .\" Since the Linux kernel and libraries are constantly changing, this |
13 | .\" manual page may be incorrect or out-of-date. The author(s) assume no | |
14 | .\" responsibility for errors or omissions, or for damages resulting from | |
15 | .\" the use of the information contained herein. The author(s) may not | |
16 | .\" have taken the same level of care in the production of this manual, | |
17 | .\" which is licensed free of charge, as they might when working | |
18 | .\" professionally. | |
c13182ef | 19 | .\" |
fea681da MK |
20 | .\" Formatted or processed versions of this manual, if unaccompanied by |
21 | .\" the source, must acknowledge the copyright and authors of this work. | |
22 | .\" | |
23 | .\" This replaces an earlier man page written by Walter Harms | |
24 | .\" <walter.harms@informatik.uni-oldenburg.de>. | |
25 | .\" | |
cc4615cc | 26 | .TH TTYSLOT 3 2007-07-26 "GNU" "Linux Programmer's Manual" |
fea681da MK |
27 | .SH NAME |
28 | ttyslot \- find the slot of the current user's terminal in some file | |
29 | .SH SYNOPSIS | |
30 | .sp | |
cc4615cc | 31 | .BR "#include <unistd.h>" " /* on BSD-like systems, and Linux */" |
fea681da | 32 | .br |
80b50848 | 33 | .BR "#include <stdlib.h>" " /* on System V-like systems */" |
fea681da MK |
34 | .sp |
35 | .B "int ttyslot(void);" | |
cc4615cc MK |
36 | .sp |
37 | .in -4n | |
38 | Feature Test Macro Requirements for glibc (see | |
39 | .BR feature_test_macros (7)): | |
40 | .in | |
41 | .sp | |
42 | .ad l | |
43 | .BR ttyslot (): | |
44 | _BSD_SOURCE || (_XOPEN_SOURCE_EXTENDED && !\ _XOPEN_SOURCE\ >=\ 500) | |
45 | .ad b | |
fea681da MK |
46 | .SH DESCRIPTION |
47 | The legacy function | |
48 | .BR ttyslot () | |
49 | returns the index of the current user's entry in some file. | |
50 | .LP | |
c13182ef MK |
51 | Now "What file?" you ask. |
52 | Well, let's first look at some history. | |
fea681da MK |
53 | .SS "Ancient History" |
54 | There used to be a file | |
55 | .I /etc/ttys | |
56 | in Unix V6, that was read by the | |
57 | .BR init (8) | |
58 | program to find out what to do with each terminal line. | |
59 | Each line consisted of three characters. | |
60 | The first character was either '0' or '1', where '0' meant "ignore". | |
61 | The second character denoted the terminal: '8' stood for "/dev/tty8". | |
62 | The third character was an argument to | |
63 | .BR getty (8) | |
8c383102 | 64 | indicating the sequence of line speeds to try ('\-' was: start trying |
c13182ef MK |
65 | 110 baud). |
66 | Thus a typical line was "18\-". | |
fea681da | 67 | A hang on some line was solved by changing the '1' to a '0', |
d9bfdb9c | 68 | signaling init, changing back again, and signaling init again. |
fea681da MK |
69 | .LP |
70 | In Unix V7 the format was changed: here the second character | |
71 | was the argument to | |
72 | .BR getty (8) | |
73 | indicating the sequence of line speeds to try ('0' was: cycle through | |
74 | 300-1200-150-110 baud; '4' was for the on-line console DECwriter) | |
75 | while the rest of the line contained the name of the tty. | |
76 | Thus a typical line was "14console". | |
77 | .LP | |
78 | Later systems have more elaborate syntax. | |
80b50848 | 79 | System V-like systems have |
fea681da MK |
80 | .I /etc/inittab |
81 | instead. | |
82 | .SS "Ancient History (2)" | |
83 | On the other hand, there is the file | |
84 | .I /etc/utmp | |
c13182ef MK |
85 | listing the people currently logged in. |
86 | It is maintained by | |
fea681da MK |
87 | .BR login (8). |
88 | It has a fixed size, and the appropriate index in the file was | |
89 | determined by | |
90 | .BR login (8) | |
91 | using the | |
92 | .BR ttyslot () | |
93 | call to find the number of the line in | |
0daa9e92 | 94 | .I /etc/ttys |
fea681da MK |
95 | (counting from 1). |
96 | .SS "The semantics of ttyslot" | |
97 | Thus, the function | |
98 | .BR ttyslot () | |
99 | returns the index of the controlling terminal of the current process | |
100 | in the file | |
101 | .IR /etc/ttys , | |
102 | and that is (usually) the same as the index of the entry for the | |
103 | current user in the file | |
104 | .IR /etc/utmp . | |
105 | BSD still has the | |
106 | .I /etc/ttys | |
80b50848 | 107 | file, but System V-like systems do not, and hence cannot refer to it. |
fea681da MK |
108 | Thus, on such systems the documentation says that |
109 | .BR ttyslot () | |
110 | returns the current user's index in the user accounting data base. | |
111 | .SH "RETURN VALUE" | |
112 | If successful, this function returns the slot number. | |
113 | On error (e.g., if none of the file descriptors 0, 1 or 2 is | |
114 | associated with a terminal that occurs in this data base) | |
115 | it returns 0 on Unix V6 and V7 and BSD-like systems, | |
80b50848 | 116 | but \-1 on System V-like systems. |
2b2581ee MK |
117 | .SH "CONFORMING TO" |
118 | SUSv1; marked as LECACY in SUSv2; removed in POSIX.1-2001. | |
119 | SUSv2 requires \-1 on error. | |
fea681da MK |
120 | .SH NOTES |
121 | The utmp file is found various places on various systems, such as | |
122 | .IR /etc/utmp , | |
123 | .IR /var/adm/utmp , | |
124 | .IR /var/run/utmp . | |
125 | .LP | |
126 | The glibc2 implementation of this function reads the file | |
127 | .BR _PATH_TTYS , | |
128 | defined in | |
129 | .I <ttyent.h> | |
c13182ef MK |
130 | as "/etc/ttys". |
131 | It returns 0 on error. | |
fea681da MK |
132 | Since Linux systems do not usually have "/etc/ttys", it will |
133 | always return 0. | |
134 | .LP | |
135 | Minix also has | |
136 | .IR fttyslot ( fd ). | |
889829be MK |
137 | .\" .SH HISTORY |
138 | .\" .BR ttyslot () | |
139 | .\" appeared in Unix V7. | |
fea681da MK |
140 | .SH "SEE ALSO" |
141 | .BR getttyent (3), | |
142 | .BR ttyname (3), | |
143 | .BR utmp (5) |