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1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
2 .\"
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13 .\" Since the Linux kernel and libraries are constantly changing, this
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24 .\"
25 .\" References consulted:
26 .\" Linux libc source code
27 .\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
28 .\" 386BSD man pages
29 .\" Modified Sat Jul 24 19:29:54 1993 by Rik Faith (faith@cs.unc.edu)
30 .TH GETGRENT 3 2017-07-13 "" "Linux Programmer's Manual"
31 .SH NAME
32 getgrent, setgrent, endgrent \- get group file entry
33 .SH SYNOPSIS
34 .nf
35 .B #include <sys/types.h>
36 .B #include <grp.h>
37 .sp
38 .B struct group *getgrent(void);
39 .sp
40 .B void setgrent(void);
41 .sp
42 .B void endgrent(void);
43 .fi
44 .PP
45 .in -4n
46 Feature Test Macro Requirements for glibc (see
47 .BR feature_test_macros (7)):
48 .in
49 .PP
50 .PD 0
51 .ad l
52 .BR setgrent ():
53 .RS 4
54 _XOPEN_SOURCE\ >=\ 500
55 .\" || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
56 || /* Glibc since 2.19: */ _DEFAULT_SOURCE
57 || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
58 .RE
59 .PP
60 .BR getgrent (),
61 .BR endgrent ():
62 .RS 4
63 Since glibc 2.22:
64 _XOPEN_SOURCE\ >=\ 500 ||
65 .\" || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
66 _DEFAULT_SOURCE
67 .br
68 Glibc 2.21 and earlier
69 _XOPEN_SOURCE\ >=\ 500
70 .\" || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
71 || /* Since glibc 2.12: */ _POSIX_C_SOURCE\ >=\ 200809L
72 || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
73 .RE
74 .PD
75 .ad b
76 .SH DESCRIPTION
77 The
78 .BR getgrent ()
79 function returns a pointer to a structure containing
80 the broken-out fields of a record in the group database
81 (e.g., the local group file
82 .IR /etc/group ,
83 NIS, and LDAP).
84 The first time
85 .BR getgrent ()
86 is called,
87 it returns the first entry; thereafter, it returns successive entries.
88 .PP
89 The
90 .BR setgrent ()
91 function rewinds to the beginning
92 of the group database, to allow repeated scans.
93 .PP
94 The
95 .BR endgrent ()
96 function is used to close the group database
97 after all processing has been performed.
98 .PP
99 The \fIgroup\fP structure is defined in \fI<grp.h>\fP as follows:
100 .PP
101 .in +4n
102 .nf
103 struct group {
104 char *gr_name; /* group name */
105 char *gr_passwd; /* group password */
106 gid_t gr_gid; /* group ID */
107 char **gr_mem; /* NULL-terminated array of pointers
108 to names of group members */
109 };
110 .fi
111 .in
112 .PP
113 For more information about the fields of this structure, see
114 .BR group (5).
115 .SH RETURN VALUE
116 The
117 .BR getgrent ()
118 function returns a pointer to a
119 .I group
120 structure,
121 or NULL if there are no more entries or an error occurs.
122 .LP
123 Upon error,
124 .I errno
125 may be set.
126 If one wants to check
127 .I errno
128 after the call, it should be set to zero before the call.
129 .PP
130 The return value may point to a static area, and may be overwritten
131 by subsequent calls to
132 .BR getgrent (),
133 .BR getgrgid (3),
134 or
135 .BR getgrnam (3).
136 (Do not pass the returned pointer to
137 .BR free (3).)
138 .SH ERRORS
139 .TP
140 .B EAGAIN
141 The service was temporarily unavailable; try again later.
142 For NSS backends in glibc this indicates a temporary error talking to the backend.
143 The error may correct itself, retrying later is suggested.
144 .TP
145 .B EINTR
146 A signal was caught; see
147 .BR signal (7).
148 .TP
149 .B EIO
150 I/O error.
151 .TP
152 .B EMFILE
153 The per-process limit on the number of open file descriptors has been reached.
154 .TP
155 .B ENFILE
156 The system-wide limit on the total number of open files has been reached.
157 .TP
158 .\" not in POSIX
159 .B ENOENT
160 A necessary input file cannot be found.
161 For NSS backends in glibc this indicates the backend is not correctly configured.
162 .TP
163 .B ENOMEM
164 .\" not in POSIX
165 Insufficient memory to allocate
166 .I group
167 structure.
168 .TP
169 .B ERANGE
170 Insufficient buffer space supplied.
171 .SH FILES
172 .TP
173 .I /etc/group
174 local group database file
175 .SH ATTRIBUTES
176 For an explanation of the terms used in this section, see
177 .BR attributes (7).
178 .TS
179 allbox;
180 lbw11 lb lb
181 l l l.
182 Interface Attribute Value
183 T{
184 .BR getgrent ()
185 T} Thread safety T{
186 MT-Unsafe race:grent
187 .br
188 race:grentbuf locale
189 T}
190 T{
191 .BR setgrent (),
192 .BR endgrent ()
193 T} Thread safety MT-Unsafe race:grent locale
194 .TE
195 .PP
196 In the above table,
197 .I grent
198 in
199 .I race:grent
200 signifies that if any of the functions
201 .BR setgrent (),
202 .BR getgrent (),
203 or
204 .BR endgrent ()
205 are used in parallel in different threads of a program,
206 then data races could occur.
207 .SH CONFORMING TO
208 POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.
209 .SH SEE ALSO
210 .BR fgetgrent (3),
211 .BR getgrent_r (3),
212 .BR getgrgid (3),
213 .BR getgrnam (3),
214 .BR getgrouplist (3),
215 .BR putgrent (3),
216 .BR group (5)