getgrgid(3)

1GETGRNAM(3)                Linux Programmer's Manual               GETGRNAM(3)
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NAME

6       getgrnam, getgrnam_r, getgrgid, getgrgid_r - get group file entry
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SYNOPSIS

9       #include <sys/types.h>
10       #include <grp.h>
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12       struct group *getgrnam(const char *name);
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14       struct group *getgrgid(gid_t gid);
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16       int getgrnam_r(const char *name, struct group *grp,
17                 char *buf, size_t buflen, struct group **result);
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19       int getgrgid_r(gid_t gid, struct group *grp,
20                 char *buf, size_t buflen, struct group **result);
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22   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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24       getgrnam_r(), getgrgid_r():
25           _POSIX_C_SOURCE >= 1 || _XOPEN_SOURCE || _BSD_SOURCE ||
26           _SVID_SOURCE || _POSIX_SOURCE
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DESCRIPTION

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.
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33       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.
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37       The group structure is defined in <grp.h> as follows:
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39           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;        /* group members */
44           };
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46       For more information about the fields of this structure, see group(5).
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48       The getgrnam_r() and getgrgid_r() functions obtain the same information
49       as  getgrnam()  and getgrgid(), but store the retrieved group structure
50       in the space pointed to by grp.  The string fields pointed  to  by  the
51       members  of  the  group  structure are stored in the buffer buf of size
52       buflen.  A pointer to the result (in case of success) or NULL (in  case
53       no entry was found or an error occurred) is stored in *result.
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55       The call
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57           sysconf(_SC_GETGR_R_SIZE_MAX)
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59       returns either -1, without changing errno, or an initial suggested size
60       for buf.  (If this size is too small, the call fails  with  ERANGE,  in
61       which case the caller can retry with a larger buffer.)
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RETURN VALUE

64       The  getgrnam()  and  getgrgid()  functions return a pointer to a group
65       structure, or NULL if the matching entry  is  not  found  or  an  error
66       occurs.   If an error occurs, errno is set appropriately.  If one wants
67       to check errno after the call, it should be  set  to  zero  before  the
68       call.
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70       The  return value may point to a static area, and may be overwritten by
71       subsequent calls to getgrent(3), getgrgid(), or  getgrnam().   (Do  not
72       pass the returned pointer to free(3).)
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74       On  success, getgrnam_r() and getgrgid_r() return zero, and set *result
75       to grp.  If no matching group record was found, these functions  return
76       0  and  store  NULL  in  *result.  In case of error, an error number is
77       returned, and NULL is stored in *result.
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ERRORS

80       0 or ENOENT or ESRCH or EBADF or EPERM or ...
81              The given name or gid was not found.
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83       EINTR  A signal was caught.
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85       EIO    I/O error.
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87       EMFILE The maximum number (OPEN_MAX) of files was open already  in  the
88              calling process.
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90       ENFILE The maximum number of files was open already in the system.
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92       ENOMEM Insufficient memory to allocate group structure.
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94       ERANGE Insufficient buffer space supplied.
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FILES

97       /etc/group
98              local group database file
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ATTRIBUTES

101   Multithreading (see pthreads(7))
102       The getgrnam() and getgrgid() functions are not thread-safe.
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104       The getgrnam_r() and getgrgid_r() functions are thread-safe.
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CONFORMING TO

107       SVr4, 4.3BSD, POSIX.1-2001.
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NOTES

110       The  formulation given above under "RETURN VALUE" is from POSIX.1-2001.
111       It does not call "not found" an error,  hence  does  not  specify  what
112       value errno might have in this situation.  But that makes it impossible
113       to recognize errors.  One might argue that  according  to  POSIX  errno
114       should be left unchanged if an entry is not found.  Experiments on var‐
115       ious UNIX-like systems shows that lots of  different  values  occur  in
116       this  situation: 0, ENOENT, EBADF, ESRCH, EWOULDBLOCK, EPERM and proba‐
117       bly others.
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COLOPHON

124       This  page  is  part of release 3.53 of the Linux man-pages project.  A
125       description of the project, and information about reporting  bugs,  can
126       be found at http://www.kernel.org/doc/man-pages/.
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130                                  2013-07-22                       GETGRNAM(3)