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bf5a7247 | 1 | .\" Copyright (c) 1993 by Thomas Koenig (ig25@rz.uni-karlsruhe.de) |
fea681da | 2 | .\" |
93015253 | 3 | .\" %%%LICENSE_START(VERBATIM) |
fea681da MK |
4 | .\" Permission is granted to make and distribute verbatim copies of this |
5 | .\" manual provided the copyright notice and this permission notice are | |
6 | .\" preserved on all copies. | |
7 | .\" | |
8 | .\" Permission is granted to copy and distribute modified versions of this | |
9 | .\" manual under the conditions for verbatim copying, provided that the | |
10 | .\" entire resulting derived work is distributed under the terms of a | |
11 | .\" permission notice identical to this one. | |
c13182ef | 12 | .\" |
fea681da MK |
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14 | .\" manual page may be incorrect or out-of-date.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 | .\" |
fea681da MK |
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 |
c08df37a | 24 | .\" |
fea681da | 25 | .\" Modified Sat Jul 24 19:53:02 1993 by Rik Faith (faith@cs.unc.edu) |
0ff49055 | 26 | .\" |
c13182ef | 27 | .\" FIXME Many more values for 'name' are supported, some of which |
0ff49055 MK |
28 | .\" are documented under 'info confstr'. |
29 | .\" See <bits/confname.h> for the rest. | |
30 | .\" These should all be added to this page. | |
31 | .\" See also the POSIX.1-2001 specification of confstr() | |
bea08fec | 32 | .\" |
4b8c67d9 | 33 | .TH CONFSTR 3 2017-09-15 "GNU" "Linux Programmer's Manual" |
fea681da MK |
34 | .SH NAME |
35 | confstr \- get configuration dependent string variables | |
36 | .SH SYNOPSIS | |
37 | .nf | |
fea681da | 38 | .B #include <unistd.h> |
68e4db0a | 39 | .PP |
fea681da MK |
40 | .BI "size_t confstr(int " "name" ", char *" buf ", size_t " len ); |
41 | .fi | |
68e4db0a | 42 | .PP |
cc4615cc MK |
43 | .in -4n |
44 | Feature Test Macro Requirements for glibc (see | |
45 | .BR feature_test_macros (7)): | |
46 | .in | |
68e4db0a | 47 | .PP |
e313308d MK |
48 | .BR confstr (): |
49 | _POSIX_C_SOURCE\ >=\ 2 || _XOPEN_SOURCE | |
fea681da | 50 | .SH DESCRIPTION |
63aa9df0 | 51 | .BR confstr () |
fea681da MK |
52 | gets the value of configuration-dependent string variables. |
53 | .PP | |
54 | The | |
55 | .I name | |
56 | argument is the system variable to be queried. | |
57 | The following variables are supported: | |
58 | .TP | |
5984622e MK |
59 | .BR _CS_GNU_LIBC_VERSION " (GNU C library only; since glibc 2.3.2)" |
60 | A string which identifies the GNU C library version on this system | |
d1f84ed7 | 61 | (e.g., "glibc 2.3.4"). |
5984622e MK |
62 | .TP |
63 | .BR _CS_GNU_LIBPTHREAD_VERSION " (GNU C library only; since glibc 2.3.2)" | |
64 | A string which identifies the POSIX implementation supplied by this | |
d1f84ed7 | 65 | C library (e.g., "NPTL 2.3.4" or "linuxthreads-0.10"). |
5984622e | 66 | .TP |
fea681da MK |
67 | .B _CS_PATH |
68 | A value for the | |
69 | .B PATH | |
70 | variable which indicates where all the POSIX.2 standard utilities can | |
71 | be found. | |
72 | .PP | |
73 | If | |
74 | .I buf | |
c13182ef | 75 | is not NULL and |
fea681da MK |
76 | .I len |
77 | is not zero, | |
63aa9df0 | 78 | .BR confstr () |
fea681da MK |
79 | copies the value of the string to |
80 | .I buf | |
81 | truncated to | |
82 | .I len \- 1 | |
a00b7454 | 83 | bytes if necessary, with a null byte (\(aq\\0\(aq) as terminator. |
fea681da | 84 | This can be detected by comparing the return value of |
63aa9df0 | 85 | .BR confstr () |
fea681da MK |
86 | against |
87 | .IR len . | |
88 | .PP | |
89 | If | |
90 | .I len | |
91 | is zero and | |
92 | .I buf | |
8478ee02 | 93 | is NULL, |
63aa9df0 | 94 | .BR confstr () |
fea681da | 95 | just returns the value as defined below. |
47297adb | 96 | .SH RETURN VALUE |
fea681da MK |
97 | If |
98 | .I name | |
4f43f21f | 99 | is a valid configuration variable, |
63aa9df0 | 100 | .BR confstr () |
c13182ef | 101 | returns the number of bytes (including the terminating null byte) |
4f43f21f MK |
102 | that would be required to hold the entire value of that variable. |
103 | This value may be greater than | |
104 | .IR len , | |
105 | which means that the value in | |
106 | .I buf | |
107 | is truncated. | |
847e0d88 | 108 | .PP |
4f43f21f | 109 | If |
c13182ef MK |
110 | .I name |
111 | is a valid configuration variable, | |
4f43f21f | 112 | but that variable does not have a value, then |
01a81d11 | 113 | .BR confstr () |
fea681da | 114 | returns 0. |
4f43f21f MK |
115 | If |
116 | .I name | |
117 | does not correspond to a valid configuration variable, | |
118 | .BR confstr () | |
119 | returns 0, and | |
120 | .I errno | |
c13182ef | 121 | is set to |
4f43f21f MK |
122 | .BR EINVAL . |
123 | .SH ERRORS | |
01a81d11 | 124 | .TP |
0daa9e92 | 125 | .B EINVAL |
078ac12d | 126 | The value of |
4f43f21f MK |
127 | .I name |
128 | is invalid. | |
a2fac97f MS |
129 | .SH ATTRIBUTES |
130 | For an explanation of the terms used in this section, see | |
131 | .BR attributes (7). | |
132 | .TS | |
133 | allbox; | |
134 | lb lb lb | |
135 | l l l. | |
136 | Interface Attribute Value | |
137 | T{ | |
138 | .BR confstr () | |
139 | T} Thread safety MT-Safe | |
140 | .TE | |
47297adb | 141 | .SH CONFORMING TO |
3e4b12f4 | 142 | POSIX.1-2001, POSIX.1-2008. |
9b336505 | 143 | .SH EXAMPLE |
fea681da MK |
144 | The following code fragment determines the path where to find |
145 | the POSIX.2 system utilities: | |
e646a1ba | 146 | .PP |
088a639b | 147 | .in +4n |
e646a1ba | 148 | .EX |
6cd17cde MK |
149 | char *pathbuf; |
150 | size_t n; | |
fea681da | 151 | |
06f38b2f | 152 | n = confstr(_CS_PATH, NULL, (size_t) 0); |
6cd17cde MK |
153 | pathbuf = malloc(n); |
154 | if (pathbuf == NULL) | |
155 | abort(); | |
fea681da | 156 | confstr(_CS_PATH, pathbuf, n); |
b8302363 | 157 | .EE |
e646a1ba | 158 | .in |
47297adb | 159 | .SH SEE ALSO |
7117b535 | 160 | .BR getconf (1), |
fea681da MK |
161 | .BR sh (1), |
162 | .BR exec (3), | |
95e77601 MK |
163 | .BR fpathconf (3), |
164 | .BR pathconf (3), | |
165 | .BR sysconf (3), | |
cc4615cc | 166 | .BR system (3) |