1GETGRENT(3) Linux Programmer's Manual GETGRENT(3)
2
6 getgrent, setgrent, endgrent - get group file entry
7
9 #include <sys/types.h>
10 #include <grp.h>
11 struct group *getgrent(void);
13 void setgrent(void);
15 void endgrent(void);
17 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
19 setgrent():
21 _XOPEN_SOURCE >= 500
22 || /* Glibc since 2.19: */ _DEFAULT_SOURCE
23 || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
24 getgrent(), endgrent():
25 Since glibc 2.22:
26 _XOPEN_SOURCE >= 500 ||
27 _DEFAULT_SOURCE
28 Glibc 2.21 and earlier
29 _XOPEN_SOURCE >= 500
30 || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L
31 || /* Glibc versions <= 2.19: */ _BSD_SOURCE ||
32 _SVID_SOURCE
33
35 The getgrent() function returns a pointer to a structure containing the
36 broken-out fields of a record in the group database (e.g., the local
37 group file /etc/group, NIS, and LDAP). The first time getgrent() is
38 called, it returns the first entry; thereafter, it returns successive
39 entries.
40 The setgrent() function rewinds to the beginning of the group database,
42 to allow repeated scans.
43 The endgrent() function is used to close the group database after all
45 processing has been performed.
46 The group structure is defined in <grp.h> as follows:
48 struct group {
50 char *gr_name; /* group name */
51 char *gr_passwd; /* group password */
52 gid_t gr_gid; /* group ID */
53 char **gr_mem; /* NULL-terminated array of pointers
54 to names of group members */
55 };
56 For more information about the fields of this structure, see group(5).
58
60 The getgrent() function returns a pointer to a group structure, or NULL
61 if there are no more entries or an error occurs.
62 Upon error, errno may be set. If one wants to check errno after the
64 call, it should be set to zero before the call.
65 The return value may point to a static area, and may be overwritten by
67 subsequent calls to getgrent(), getgrgid(3), or getgrnam(3). (Do not
68 pass the returned pointer to free(3).)
69
71 EAGAIN The service was temporarily unavailable; try again later. For
72 NSS backends in glibc this indicates a temporary error talking
73 to the backend. The error may correct itself, retrying later is
74 suggested.
75 EINTR A signal was caught; see signal(7).
77 EIO I/O error.
79 EMFILE The per-process limit on the number of open file descriptors has
81 been reached.
82 ENFILE The system-wide limit on the total number of open files has been
84 reached.
85 ENOENT A necessary input file cannot be found. For NSS backends in
87 glibc this indicates the backend is not correctly configured.
88 ENOMEM Insufficient memory to allocate group structure.
90 ERANGE Insufficient buffer space supplied.
92
94 /etc/group
95 local group database file
96
98 For an explanation of the terms used in this section, see at‐
99 tributes(7).
100 ┌────────────┬───────────────┬─────────────────────────────┐
102 │Interface │ Attribute │ Value │
103 ├────────────┼───────────────┼─────────────────────────────┤
104 │getgrent() │ Thread safety │ MT-Unsafe race:grent │
105 │ │ │ race:grentbuf locale │
106 ├────────────┼───────────────┼─────────────────────────────┤
107 │setgrent(), │ Thread safety │ MT-Unsafe race:grent locale │
108 │endgrent() │ │ │
109 └────────────┴───────────────┴─────────────────────────────┘
110 In the above table, grent in race:grent signifies that if any of the
111 functions setgrent(), getgrent(), or endgrent() are used in parallel in
112 different threads of a program, then data races could occur.
113
115 POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.
116
118 fgetgrent(3), getgrent_r(3), getgrgid(3), getgrnam(3), getgrouplist(3),
119 putgrent(3), group(5)
120
122 This page is part of release 5.10 of the Linux man-pages project. A
123 description of the project, information about reporting bugs, and the
124 latest version of this page, can be found at
125 https://www.kernel.org/doc/man-pages/.
126 2017-09-15 GETGRENT(3)