getgrent(3)

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

6       getgrent, setgrent, endgrent - 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 *getgrent(void);
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14       void setgrent(void);
15       void endgrent(void);
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17   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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19       setgrent():
20           _XOPEN_SOURCE >= 500
21               || /* Glibc since 2.19: */ _DEFAULT_SOURCE
22               || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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24       getgrent(), endgrent():
25           Since glibc 2.22:
26               _XOPEN_SOURCE >= 500 || _DEFAULT_SOURCE
27           Glibc 2.21 and earlier
28               _XOPEN_SOURCE >= 500
29                   || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L
30                   || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
31

DESCRIPTION

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

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

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

92       /etc/group
93              local group database file
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ATTRIBUTES

96       For  an  explanation  of  the  terms  used  in  this  section,  see at‐
97       tributes(7).
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99       ┌────────────┬───────────────┬─────────────────────────────────────────┐
100       │Interface   │ Attribute     │ Value                                   │
101       ├────────────┼───────────────┼─────────────────────────────────────────┤
102       │getgrent()  │ Thread safety │ MT-Unsafe race:grent race:grentbuf      │
103       │            │               │ locale                                  │
104       ├────────────┼───────────────┼─────────────────────────────────────────┤
105       │setgrent(), │ Thread safety │ MT-Unsafe race:grent locale             │
106       │endgrent()  │               │                                         │
107       └────────────┴───────────────┴─────────────────────────────────────────┘
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109       In the above table, grent in race:grent signifies that if  any  of  the
110       functions setgrent(), getgrent(), or endgrent() are used in parallel in
111       different threads of a program, then data races could occur.
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CONFORMING TO

114       POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.
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COLOPHON

121       This  page  is  part of release 5.12 of the Linux man-pages project.  A
122       description of the project, information about reporting bugs,  and  the
123       latest     version     of     this    page,    can    be    found    at
124       https://www.kernel.org/doc/man-pages/.
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128                                  2021-03-22                       GETGRENT(3)