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1 | .\" Copyright (c) 2003 Andries Brouwer (aeb@cwi.nl) |
2 | .\" | |
1dd72f9c | 3 | .\" %%%LICENSE_START(GPLv2+_DOC_FULL) |
fea681da MK |
4 | .\" This is free documentation; you can redistribute it and/or |
5 | .\" modify it under the terms of the GNU General Public License as | |
6 | .\" published by the Free Software Foundation; either version 2 of | |
7 | .\" the License, or (at your option) any later version. | |
8 | .\" | |
9 | .\" The GNU General Public License's references to "object code" | |
10 | .\" and "executables" are to be interpreted as the output of any | |
11 | .\" document formatting or typesetting system, including | |
12 | .\" intermediate and printed output. | |
13 | .\" | |
14 | .\" This manual is distributed in the hope that it will be useful, | |
15 | .\" but WITHOUT ANY WARRANTY; without even the implied warranty of | |
16 | .\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
17 | .\" GNU General Public License for more details. | |
18 | .\" | |
19 | .\" You should have received a copy of the GNU General Public | |
c715f741 MK |
20 | .\" License along with this manual; if not, see |
21 | .\" <http://www.gnu.org/licenses/>. | |
6a8d8745 | 22 | .\" %%%LICENSE_END |
fea681da | 23 | .\" |
4b8c67d9 | 24 | .TH GETGRENT_R 3 2017-09-15 "GNU" "Linux Programmer's Manual" |
fea681da MK |
25 | .SH NAME |
26 | getgrent_r, fgetgrent_r \- get group file entry reentrantly | |
27 | .SH SYNOPSIS | |
28 | .nf | |
fea681da | 29 | .B #include <grp.h> |
68e4db0a | 30 | .PP |
fea681da | 31 | .BI "int getgrent_r(struct group *" gbuf ", char *" buf , |
fea681da | 32 | .BI " size_t " buflen ", struct group **" gbufp ); |
68e4db0a | 33 | .PP |
e164e983 | 34 | .BI "int fgetgrent_r(FILE *" stream ", struct group *" gbuf ", char *" buf , |
fea681da | 35 | .BI " size_t " buflen ", struct group **" gbufp ); |
cc4615cc | 36 | .fi |
68e4db0a | 37 | .PP |
cc4615cc MK |
38 | .in -4n |
39 | Feature Test Macro Requirements for glibc (see | |
40 | .BR feature_test_macros (7)): | |
41 | .in | |
68e4db0a | 42 | .PP |
cc4615cc MK |
43 | .BR getgrent_r (): |
44 | _GNU_SOURCE | |
45 | .\" FIXME . The FTM requirements seem inconsistent here. File a glibc bug? | |
46 | .br | |
47 | .BR fgetgrent_r (): | |
51c612fb MK |
48 | Since glibc 2.19: |
49 | _DEFAULT_SOURCE | |
50 | Glibc 2.19 and earlier: | |
51 | _SVID_SOURCE | |
fea681da MK |
52 | .SH DESCRIPTION |
53 | The functions | |
63aa9df0 | 54 | .BR getgrent_r () |
fea681da | 55 | and |
63aa9df0 | 56 | .BR fgetgrent_r () |
fea681da MK |
57 | are the reentrant versions of |
58 | .BR getgrent (3) | |
59 | and | |
60 | .BR fgetgrent (3). | |
61 | The former reads the next group entry from the stream initialized by | |
62 | .BR setgrent (3). | |
43905c28 | 63 | The latter reads the next group entry from |
e164e983 | 64 | .IR stream . |
fea681da MK |
65 | .PP |
66 | The \fIgroup\fP structure is defined in | |
67 | .I <grp.h> | |
68 | as follows: | |
51f5698d | 69 | .PP |
bd191423 | 70 | .in +4n |
b8302363 | 71 | .EX |
fea681da | 72 | struct group { |
5e333b1b MK |
73 | char *gr_name; /* group name */ |
74 | char *gr_passwd; /* group password */ | |
75 | gid_t gr_gid; /* group ID */ | |
b7800b44 MK |
76 | char **gr_mem; /* NULL-terminated array of pointers |
77 | to names of group members */ | |
fea681da | 78 | }; |
b8302363 | 79 | .EE |
bd191423 | 80 | .in |
b39f3e05 MK |
81 | .PP |
82 | For more information about the fields of this structure, see | |
83 | .BR group (5). | |
84 | .PP | |
54d75d6c | 85 | The nonreentrant functions return a pointer to static storage, |
fea681da MK |
86 | where this static storage contains further pointers to group |
87 | name, password and members. | |
88 | The reentrant functions described here return all of that in | |
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89 | caller-provided buffers. |
90 | First of all there is the buffer | |
fea681da | 91 | .I gbuf |
0c2ec4f1 | 92 | that can hold a \fIstruct group\fP. |
c13182ef | 93 | And next the buffer |
fea681da MK |
94 | .I buf |
95 | of size | |
96 | .I buflen | |
97 | that can hold additional strings. | |
0c2ec4f1 | 98 | The result of these functions, the \fIstruct group\fP read from the stream, |
fea681da | 99 | is stored in the provided buffer |
bd9b2a9c | 100 | .IR *gbuf , |
0c2ec4f1 | 101 | and a pointer to this \fIstruct group\fP is returned in |
bd9b2a9c | 102 | .IR *gbufp . |
47297adb | 103 | .SH RETURN VALUE |
fea681da | 104 | On success, these functions return 0 and |
bd9b2a9c | 105 | .I *gbufp |
0c2ec4f1 | 106 | is a pointer to the \fIstruct group\fP. |
fea681da | 107 | On error, these functions return an error value and |
bd9b2a9c | 108 | .I *gbufp |
fea681da MK |
109 | is NULL. |
110 | .SH ERRORS | |
111 | .TP | |
112 | .B ENOENT | |
113 | No more entries. | |
114 | .TP | |
115 | .B ERANGE | |
c13182ef MK |
116 | Insufficient buffer space supplied. |
117 | Try again with larger buffer. | |
f8c46262 ZL |
118 | .SH ATTRIBUTES |
119 | For an explanation of the terms used in this section, see | |
120 | .BR attributes (7). | |
121 | .TS | |
122 | allbox; | |
123 | lb lb lbw27 | |
124 | l l l. | |
125 | Interface Attribute Value | |
126 | T{ | |
127 | .BR getgrent_r () | |
128 | T} Thread safety MT-Unsafe race:grent locale | |
129 | T{ | |
130 | .BR fgetgrent_r () | |
131 | T} Thread safety MT-Safe | |
132 | .TE | |
847e0d88 | 133 | .sp 1 |
f8c46262 ZL |
134 | In the above table, |
135 | .I grent | |
136 | in | |
137 | .I race:grent | |
138 | signifies that if any of the functions | |
139 | .BR setgrent (), | |
140 | .BR getgrent (), | |
141 | .BR endgrent (), | |
142 | or | |
143 | .BR getgrent_r () | |
144 | are used in parallel in different threads of a program, | |
145 | then data races could occur. | |
47297adb | 146 | .SH CONFORMING TO |
2b2581ee MK |
147 | These functions are GNU extensions, done in a style resembling |
148 | the POSIX version of functions like | |
149 | .BR getpwnam_r (3). | |
b33e5e80 | 150 | Other systems use the prototype |
51f5698d | 151 | .PP |
088a639b | 152 | .in +4n |
b8302363 | 153 | .EX |
3f282501 MK |
154 | struct group *getgrent_r(struct group *grp, char *buf, |
155 | int buflen); | |
b8302363 | 156 | .EE |
bdd915e2 | 157 | .in |
51f5698d | 158 | .PP |
2b2581ee | 159 | or, better, |
51f5698d | 160 | .PP |
088a639b | 161 | .in +4n |
b8302363 | 162 | .EX |
3f282501 MK |
163 | int getgrent_r(struct group *grp, char *buf, int buflen, |
164 | FILE **gr_fp); | |
b8302363 | 165 | .EE |
bdd915e2 | 166 | .in |
2b2581ee MK |
167 | .SH NOTES |
168 | The function | |
169 | .BR getgrent_r () | |
170 | is not really reentrant since it shares the reading position | |
171 | in the stream with all other threads. | |
fea681da | 172 | .SH EXAMPLE |
bdd915e2 | 173 | .EX |
fea681da MK |
174 | #define _GNU_SOURCE |
175 | #include <grp.h> | |
176 | #include <stdio.h> | |
af9c7ff2 | 177 | #include <stdlib.h> |
fea681da MK |
178 | #define BUFLEN 4096 |
179 | ||
c13182ef MK |
180 | int |
181 | main(void) | |
cf0a9ace MK |
182 | { |
183 | struct group grp, *grpp; | |
184 | char buf[BUFLEN]; | |
185 | int i; | |
fea681da | 186 | |
cf0a9ace MK |
187 | setgrent(); |
188 | while (1) { | |
189 | i = getgrent_r(&grp, buf, BUFLEN, &grpp); | |
190 | if (i) | |
191 | break; | |
29059a65 | 192 | printf("%s (%d):", grpp\->gr_name, grpp\->gr_gid); |
cf0a9ace | 193 | for (i = 0; ; i++) { |
29059a65 | 194 | if (grpp\->gr_mem[i] == NULL) |
cf0a9ace | 195 | break; |
29059a65 | 196 | printf(" %s", grpp\->gr_mem[i]); |
cf0a9ace | 197 | } |
31a6818e | 198 | printf("\en"); |
cf0a9ace MK |
199 | } |
200 | endgrent(); | |
5bc8c34c | 201 | exit(EXIT_SUCCESS); |
fea681da | 202 | } |
bdd915e2 | 203 | .EE |
fea681da MK |
204 | .\" perhaps add error checking - should use strerror_r |
205 | .\" #include <errno.h> | |
206 | .\" #include <stdlib.h> | |
207 | .\" if (i) { | |
208 | .\" if (i == ENOENT) | |
209 | .\" break; | |
210 | .\" printf("getgrent_r: %s", strerror(i)); | |
4c44ffe5 | 211 | .\" exit(EXIT_FAILURE); |
fea681da | 212 | .\" } |
47297adb | 213 | .SH SEE ALSO |
fea681da MK |
214 | .BR fgetgrent (3), |
215 | .BR getgrent (3), | |
216 | .BR getgrgid (3), | |
217 | .BR getgrnam (3), | |
c9c3b6f3 | 218 | .BR putgrent (3), |
cc4615cc | 219 | .BR group (5) |