getgrnam(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 *gbuf,
17                 char *buf, size_t buflen, struct group **gbufp);
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19       int getgrgid_r(gid_t gid, struct group *gbuf,
20                 char *buf, size_t buflen, struct group **gbufp);
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DESCRIPTION

23       The getgrnam() function returns a pointer to a structure containing the
24       broken-out fields of the record in the group database (e.g., the  local
25       group file /etc/group, NIS, and LDAP) that matches the group name name.
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27       The getgrgid() function returns a pointer to a structure containing the
28       broken-out fields of the record in the group database that matches  the
29       group ID gid.
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31       The  getgrnam_r()  and  getgrgid_r() functions obtain the same informa‐
32       tion, but store the retrieved group structure in the space  pointed  to
33       by  gbuf.  This group structure contains pointers to strings, and these
34       strings are stored in the buffer buf of size buflen.  A pointer to  the
35       result  (in  case of success) or NULL (in case no entry was found or an
36       error occurred) is stored in *gbufp.
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38       The group structure is defined in <grp.h> as follows:
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40         struct group {
41             char   *gr_name;       /* group name */
42             char   *gr_passwd;     /* group password */
43             gid_t   gr_gid;        /* group ID */
44             char  **gr_mem;        /* group members */
45         };
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47       The maximum needed size for buf can be found using sysconf(3) with  the
48       _SC_GETGR_R_SIZE_MAX parameter.
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RETURN VALUE

51       The  getgrnam()  and  getgrgid()  functions return a pointer to a group
52       structure, or NULL if the matching entry  is  not  found  or  an  error
53       occurs.   If an error occurs, errno is set appropriately.  If one wants
54       to check errno after the call, it should be  set  to  zero  before  the
55       call.
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57       The  return  value  may point to static area, and may be overwritten by
58       subsequent calls to getgrent(), getgrgid(), or getgrnam().
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60       The  getgrnam_r() and getgrgid_r() functions return zero on success. In
61       case of error, an error number is returned.
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ERRORS

64       0 or ENOENT or ESRCH or EBADF or EPERM or ...
65              The given name or gid was not found.
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67       EINTR  A signal was caught.
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69       EIO    I/O error.
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71       EMFILE The  maximum  number (OPEN_MAX) of files was open already in the
72              calling process.
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74       ENFILE The maximum number of files was open already in the system.
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76       ENOMEM Insufficient memory to allocate group structure.
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78       ERANGE Insufficient buffer space supplied.
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FILES

81       /etc/group
82              local group database file
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CONFORMING TO

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

88       The formulation given above under "RETURN VALUE" is from  POSIX.1-2001.
89       It  does  not  call  "not  found" an error, hence does not specify what
90       value errno might have in this situation. But that makes it  impossible
91       to  recognize  errors.  One  might  argue that according to POSIX errno
92       should be left unchanged if an entry is not found. Experiments on vari‐
93       ous Unix-like systems shows that lots of different values occur in this
94       situation: 0, ENOENT, EBADF, ESRCH,  EWOULDBLOCK,  EPERM  and  probably
95       others.
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