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1 | .\" Copyright (C) 2002 Andries Brouwer <aeb@cwi.nl> |
2 | .\" | |
93015253 | 3 | .\" %%%LICENSE_START(VERBATIM) |
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4 | .\" Permission is granted to make and distribute verbatim copies of this |
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8 | .\" Permission is granted to copy and distribute modified versions of this | |
9 | .\" manual under the conditions for verbatim copying, provided that the | |
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11 | .\" permission notice identical to this one. | |
c13182ef | 12 | .\" |
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13 | .\" Since the Linux kernel and libraries are constantly changing, this |
14 | .\" manual page may be incorrect or out-of-date. The author(s) assume no | |
15 | .\" responsibility for errors or omissions, or for damages resulting from | |
16 | .\" the use of the information contained herein. The author(s) may not | |
17 | .\" have taken the same level of care in the production of this manual, | |
18 | .\" which is licensed free of charge, as they might when working | |
19 | .\" professionally. | |
c13182ef | 20 | .\" |
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21 | .\" Formatted or processed versions of this manual, if unaccompanied by |
22 | .\" the source, must acknowledge the copyright and authors of this work. | |
4b72fb64 | 23 | .\" %%%LICENSE_END |
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24 | .\" |
25 | .\" This replaces an earlier man page written by Walter Harms | |
26 | .\" <walter.harms@informatik.uni-oldenburg.de>. | |
27 | .\" | |
50831f9b | 28 | .TH TTYSLOT 3 2010-09-20 "GNU" "Linux Programmer's Manual" |
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29 | .SH NAME |
30 | ttyslot \- find the slot of the current user's terminal in some file | |
31 | .SH SYNOPSIS | |
cc4615cc | 32 | .BR "#include <unistd.h>" " /* on BSD-like systems, and Linux */" |
fea681da | 33 | .br |
80b50848 | 34 | .BR "#include <stdlib.h>" " /* on System V-like systems */" |
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35 | .sp |
36 | .B "int ttyslot(void);" | |
cc4615cc MK |
37 | .sp |
38 | .in -4n | |
39 | Feature Test Macro Requirements for glibc (see | |
40 | .BR feature_test_macros (7)): | |
41 | .in | |
42 | .sp | |
43 | .ad l | |
44 | .BR ttyslot (): | |
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45 | .RS 4 |
46 | _BSD_SOURCE || | |
47 | .br | |
7f4dc8ae | 48 | _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_\ <\ 500\ &&\ _XOPEN_SOURCE_EXTENDED |
f0644d82 | 49 | .RE |
cc4615cc | 50 | .ad b |
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51 | .SH DESCRIPTION |
52 | The legacy function | |
53 | .BR ttyslot () | |
54 | returns the index of the current user's entry in some file. | |
55 | .LP | |
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56 | Now "What file?" you ask. |
57 | Well, let's first look at some history. | |
73d8cece | 58 | .SS Ancient history |
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59 | There used to be a file |
60 | .I /etc/ttys | |
008f1ecc | 61 | in UNIX V6, that was read by the |
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62 | .BR init (8) |
63 | program to find out what to do with each terminal line. | |
64 | Each line consisted of three characters. | |
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65 | The first character was either \(aq0\(aq or \(aq1\(aq, |
66 | where \(aq0\(aq meant "ignore". | |
67 | The second character denoted the terminal: \(aq8\(aq stood for "/dev/tty8". | |
fea681da | 68 | The third character was an argument to |
d80b8255 | 69 | .BR getty (8) |
f81fb444 | 70 | indicating the sequence of line speeds to try (\(aq\-\(aq was: start trying |
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71 | 110 baud). |
72 | Thus a typical line was "18\-". | |
f81fb444 | 73 | A hang on some line was solved by changing the \(aq1\(aq to a \(aq0\(aq, |
d9bfdb9c | 74 | signaling init, changing back again, and signaling init again. |
fea681da | 75 | .LP |
008f1ecc | 76 | In UNIX V7 the format was changed: here the second character |
fea681da | 77 | was the argument to |
d80b8255 | 78 | .BR getty (8) |
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79 | indicating the sequence of line speeds to try (\(aq0\(aq was: cycle through |
80 | 300-1200-150-110 baud; \(aq4\(aq was for the on-line console DECwriter) | |
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81 | while the rest of the line contained the name of the tty. |
82 | Thus a typical line was "14console". | |
83 | .LP | |
84 | Later systems have more elaborate syntax. | |
80b50848 | 85 | System V-like systems have |
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86 | .I /etc/inittab |
87 | instead. | |
73d8cece | 88 | .SS Ancient history (2) |
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89 | On the other hand, there is the file |
90 | .I /etc/utmp | |
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91 | listing the people currently logged in. |
92 | It is maintained by | |
49ec013c | 93 | .BR login (1). |
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94 | It has a fixed size, and the appropriate index in the file was |
95 | determined by | |
49ec013c | 96 | .BR login (1) |
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97 | using the |
98 | .BR ttyslot () | |
99 | call to find the number of the line in | |
0daa9e92 | 100 | .I /etc/ttys |
fea681da | 101 | (counting from 1). |
73d8cece | 102 | .SS The semantics of ttyslot |
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103 | Thus, the function |
104 | .BR ttyslot () | |
a1ffe9f5 | 105 | returns the index of the controlling terminal of the calling process |
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106 | in the file |
107 | .IR /etc/ttys , | |
108 | and that is (usually) the same as the index of the entry for the | |
109 | current user in the file | |
110 | .IR /etc/utmp . | |
111 | BSD still has the | |
112 | .I /etc/ttys | |
80b50848 | 113 | file, but System V-like systems do not, and hence cannot refer to it. |
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114 | Thus, on such systems the documentation says that |
115 | .BR ttyslot () | |
116 | returns the current user's index in the user accounting data base. | |
47297adb | 117 | .SH RETURN VALUE |
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118 | If successful, this function returns the slot number. |
119 | On error (e.g., if none of the file descriptors 0, 1 or 2 is | |
120 | associated with a terminal that occurs in this data base) | |
008f1ecc | 121 | it returns 0 on UNIX V6 and V7 and BSD-like systems, |
80b50848 | 122 | but \-1 on System V-like systems. |
47297adb | 123 | .SH CONFORMING TO |
39ed8b54 | 124 | SUSv1; marked as LEGACY in SUSv2; removed in POSIX.1-2001. |
2b2581ee | 125 | SUSv2 requires \-1 on error. |
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126 | .SH NOTES |
127 | The utmp file is found various places on various systems, such as | |
128 | .IR /etc/utmp , | |
129 | .IR /var/adm/utmp , | |
130 | .IR /var/run/utmp . | |
131 | .LP | |
132 | The glibc2 implementation of this function reads the file | |
133 | .BR _PATH_TTYS , | |
134 | defined in | |
135 | .I <ttyent.h> | |
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136 | as "/etc/ttys". |
137 | It returns 0 on error. | |
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138 | Since Linux systems do not usually have "/etc/ttys", it will |
139 | always return 0. | |
140 | .LP | |
141 | Minix also has | |
142 | .IR fttyslot ( fd ). | |
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143 | .\" .SH HISTORY |
144 | .\" .BR ttyslot () | |
008f1ecc | 145 | .\" appeared in UNIX V7. |
47297adb | 146 | .SH SEE ALSO |
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147 | .BR getttyent (3), |
148 | .BR ttyname (3), | |
149 | .BR utmp (5) |