1GETGRNAM(3) Linux Programmer's Manual GETGRNAM(3)
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6 getgrnam, getgrnam_r, getgrgid, getgrgid_r - get group file entry
7
9 #include <sys/types.h>
10 #include <grp.h>
11 struct group *getgrnam(const char *name);
13 struct group *getgrgid(gid_t gid);
14 int getgrnam_r(const char *restrict name, struct group *restrict grp,
16 char *restrict buf, size_t buflen,
17 struct group **restrict result);
18 int getgrgid_r(gid_t gid, struct group *restrict grp,
19 char *restrict buf, size_t buflen,
20 struct group **restrict result);
21 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
23 getgrnam_r(), getgrgid_r():
25 _POSIX_C_SOURCE
26 || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
27
29 The getgrnam() function returns a pointer to a structure containing the
30 broken-out fields of the record in the group database (e.g., the local
31 group file /etc/group, NIS, and LDAP) that matches the group name name.
32 The getgrgid() function returns a pointer to a structure containing the
34 broken-out fields of the record in the group database that matches the
35 group ID gid.
36 The group structure is defined in <grp.h> as follows:
38 struct group {
40 char *gr_name; /* group name */
41 char *gr_passwd; /* group password */
42 gid_t gr_gid; /* group ID */
43 char **gr_mem; /* NULL-terminated array of pointers
44 to names of group members */
45 };
46 For more information about the fields of this structure, see group(5).
48 The getgrnam_r() and getgrgid_r() functions obtain the same information
50 as getgrnam() and getgrgid(), but store the retrieved group structure
51 in the space pointed to by grp. The string fields pointed to by the
52 members of the group structure are stored in the buffer buf of size bu‐
53 flen. A pointer to the result (in case of success) or NULL (in case no
54 entry was found or an error occurred) is stored in *result.
55 The call
57 sysconf(_SC_GETGR_R_SIZE_MAX)
59 returns either -1, without changing errno, or an initial suggested size
61 for buf. (If this size is too small, the call fails with ERANGE, in
62 which case the caller can retry with a larger buffer.)
63
65 The getgrnam() and getgrgid() functions return a pointer to a group
66 structure, or NULL if the matching entry is not found or an error oc‐
67 curs. If an error occurs, errno is set to indicate the error. If one
68 wants to check errno after the call, it should be set to zero before
69 the call.
70 The return value may point to a static area, and may be overwritten by
72 subsequent calls to getgrent(3), getgrgid(), or getgrnam(). (Do not
73 pass the returned pointer to free(3).)
74 On success, getgrnam_r() and getgrgid_r() return zero, and set *result
76 to grp. If no matching group record was found, these functions return
77 0 and store NULL in *result. In case of error, an error number is re‐
78 turned, and NULL is stored in *result.
79
81 0 or ENOENT or ESRCH or EBADF or EPERM or ...
82 The given name or gid was not found.
83 EINTR A signal was caught; see signal(7).
85 EIO I/O error.
87 EMFILE The per-process limit on the number of open file descriptors has
89 been reached.
90 ENFILE The system-wide limit on the total number of open files has been
92 reached.
93 ENOMEM Insufficient memory to allocate group structure.
95 ERANGE Insufficient buffer space supplied.
97
99 /etc/group
100 local group database file
101
103 For an explanation of the terms used in this section, see at‐
104 tributes(7).
105 ┌──────────────┬───────────────┬───────────────────────────────────────┐
107 │Interface │ Attribute │ Value │
108 ├──────────────┼───────────────┼───────────────────────────────────────┤
109 │getgrnam() │ Thread safety │ MT-Unsafe race:grnam locale │
110 ├──────────────┼───────────────┼───────────────────────────────────────┤
111 │getgrgid() │ Thread safety │ MT-Unsafe race:grgid locale │
112 ├──────────────┼───────────────┼───────────────────────────────────────┤
113 │getgrnam_r(), │ Thread safety │ MT-Safe locale │
114 │getgrgid_r() │ │ │
115 └──────────────┴───────────────┴───────────────────────────────────────┘
116
118 POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.
119
121 The formulation given above under "RETURN VALUE" is from POSIX.1. It
122 does not call "not found" an error, hence does not specify what value
123 errno might have in this situation. But that makes it impossible to
124 recognize errors. One might argue that according to POSIX errno should
125 be left unchanged if an entry is not found. Experiments on various
126 UNIX-like systems show that lots of different values occur in this sit‐
127 uation: 0, ENOENT, EBADF, ESRCH, EWOULDBLOCK, EPERM, and probably oth‐
128 ers.
129
131 endgrent(3), fgetgrent(3), getgrent(3), getpwnam(3), setgrent(3),
132 group(5)
133
135 This page is part of release 5.12 of the Linux man-pages project. A
136 description of the project, information about reporting bugs, and the
137 latest version of this page, can be found at
138 https://www.kernel.org/doc/man-pages/.
139 2021-03-22 GETGRNAM(3)