getgrent(3)

1getgrent(3)                Library Functions Manual                getgrent(3)
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NAME

6       getgrent, setgrent, endgrent - get group file entry
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LIBRARY

9       Standard C library (libc, -lc)
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SYNOPSIS

12       #include <sys/types.h>
13       #include <grp.h>
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15       struct group *getgrent(void);
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17       void setgrent(void);
18       void endgrent(void);
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20   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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22       setgrent():
23           _XOPEN_SOURCE >= 500
24               || /* glibc >= 2.19: */ _DEFAULT_SOURCE
25               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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27       getgrent(), endgrent():
28           Since glibc 2.22:
29               _XOPEN_SOURCE >= 500 || _DEFAULT_SOURCE
30           glibc 2.21 and earlier
31               _XOPEN_SOURCE >= 500
32                   || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L
33                   || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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DESCRIPTION

36       The getgrent() function returns a pointer to a structure containing the
37       broken-out fields of a record in the group database  (e.g.,  the  local
38       group  file  /etc/group,  NIS, and LDAP).  The first time getgrent() is
39       called, it returns the first entry; thereafter, it  returns  successive
40       entries.
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42       The setgrent() function rewinds to the beginning of the group database,
43       to allow repeated scans.
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45       The endgrent() function is used to close the group database  after  all
46       processing has been performed.
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48       The group structure is defined in <grp.h> as follows:
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50           struct group {
51               char   *gr_name;        /* group name */
52               char   *gr_passwd;      /* group password */
53               gid_t   gr_gid;         /* group ID */
54               char  **gr_mem;         /* NULL-terminated array of pointers
55                                          to names of group members */
56           };
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58       For more information about the fields of this structure, see group(5).
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RETURN VALUE

61       The getgrent() function returns a pointer to a group structure, or NULL
62       if there are no more entries or an error occurs.
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64       Upon error, errno may be set.  If one wants to check  errno  after  the
65       call, it should be set to zero before the call.
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67       The  return value may point to a static area, and may be overwritten by
68       subsequent calls to getgrent(), getgrgid(3), or getgrnam(3).   (Do  not
69       pass the returned pointer to free(3).)
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ERRORS

72       EAGAIN The  service  was temporarily unavailable; try again later.  For
73              NSS backends in glibc this indicates a temporary  error  talking
74              to the backend.  The error may correct itself, retrying later is
75              suggested.
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77       EINTR  A signal was caught; see signal(7).
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79       EIO    I/O error.
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81       EMFILE The per-process limit on the number of open file descriptors has
82              been reached.
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84       ENFILE The system-wide limit on the total number of open files has been
85              reached.
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87       ENOENT A necessary input file cannot be found.   For  NSS  backends  in
88              glibc this indicates the backend is not correctly configured.
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90       ENOMEM Insufficient memory to allocate group structure.
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92       ERANGE Insufficient buffer space supplied.
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FILES

95       /etc/group
96              local group database file
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ATTRIBUTES

99       For  an  explanation  of  the  terms  used  in  this  section,  see at‐
100       tributes(7).
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102       ┌────────────┬───────────────┬─────────────────────────────────────────┐
103       │Interface   │ Attribute     │ Value                                   │
104       ├────────────┼───────────────┼─────────────────────────────────────────┤
105       │getgrent()  │ Thread safety │ MT-Unsafe race:grent race:grentbuf      │
106       │            │               │ locale                                  │
107       ├────────────┼───────────────┼─────────────────────────────────────────┤
108       │setgrent(), │ Thread safety │ MT-Unsafe race:grent locale             │
109       │endgrent()  │               │                                         │
110       └────────────┴───────────────┴─────────────────────────────────────────┘
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112       In the above table, grent in race:grent signifies that if  any  of  the
113       functions setgrent(), getgrent(), or endgrent() are used in parallel in
114       different threads of a program, then data races could occur.
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STANDARDS

117       POSIX.1-2008.
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HISTORY

120       POSIX.1-2001, SVr4, 4.3BSD.
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