man3/getgrent.3

   1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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  25 .\" References consulted:
  26 .\"     Linux libc source code
  27 .\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
  28 .\"     386BSD man pages
  29 .\" Modified Sat Jul 24 19:29:54 1993 by Rik Faith (faith@cs.unc.edu)
  30 .TH GETGRENT 3  2017-09-15 "" "Linux Programmer's Manual"
  31 .SH NAME
  32 getgrent, setgrent, endgrent \- get group file entry
  33 .SH SYNOPSIS
  34 .nf
  35 .B #include <sys/types.h>
  36 .B #include <grp.h>
  37 .PP
  38 .B struct group *getgrent(void);
  39 .PP
  40 .B void setgrent(void);
  41 .PP
  42 .B void endgrent(void);
  43 .fi
  44 .PP
  45 .in -4n
  46 Feature Test Macro Requirements for glibc (see
  47 .BR feature_test_macros (7)):
  48 .in
  49 .PP
  50 .PD 0
  51 .ad l
  52 .BR setgrent ():
  53 .RS 4
  54 _XOPEN_SOURCE\ >=\ 500
  55 .\"    || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
  56     || /* Glibc since 2.19: */ _DEFAULT_SOURCE
  57     || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
  58 .RE
  59 .PP
  60 .BR getgrent (),
  61 .BR endgrent ():
  62 .RS 4
  63 Since glibc 2.22:
  64     _XOPEN_SOURCE\ >=\ 500 ||
  65 .\"        || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
  66         _DEFAULT_SOURCE
  67 .br
  68 Glibc 2.21 and earlier
  69     _XOPEN_SOURCE\ >=\ 500
  70 .\"        || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
  71         || /* Since glibc 2.12: */ _POSIX_C_SOURCE\ >=\ 200809L
  72         || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
  73 .RE
  74 .PD
  75 .ad b
  76 .SH DESCRIPTION
  77 The
  78 .BR getgrent ()
  79 function returns a pointer to a structure containing
  80 the broken-out fields of a record in the group database
  81 (e.g., the local group file
  82 .IR /etc/group ,
  83 NIS, and LDAP).
  84 The first time
  85 .BR getgrent ()
  86 is called,
  87 it returns the first entry; thereafter, it returns successive entries.
  88 .PP
  89 The
  90 .BR setgrent ()
  91 function rewinds to the beginning
  92 of the group database, to allow repeated scans.
  93 .PP
  94 The
  95 .BR endgrent ()
  96 function is used to close the group database
  97 after all processing has been performed.
  98 .PP
  99 The \fIgroup\fP structure is defined in \fI<grp.h>\fP as follows:
 100 .PP
 101 .in +4n
 102 .EX
 103 struct group {
 104     char   *gr_name;        /* group name */
 105     char   *gr_passwd;      /* group password */
 106     gid_t   gr_gid;         /* group ID */
 107     char  **gr_mem;         /* NULL-terminated array of pointers
 108                                to names of group members */
 109 };
 110 .EE
 111 .in
 112 .PP
 113 For more information about the fields of this structure, see
 114 .BR group (5).
 115 .SH RETURN VALUE
 116 The
 117 .BR getgrent ()
 118 function returns a pointer to a
 119 .I group
 120 structure,
 121 or NULL if there are no more entries or an error occurs.
 122 .PP
 123 Upon error,
 124 .I errno
 125 may be set.
 126 If one wants to check
 127 .I errno
 128 after the call, it should be set to zero before the call.
 129 .PP
 130 The return value may point to a static area, and may be overwritten
 131 by subsequent calls to
 132 .BR getgrent (),
 133 .BR getgrgid (3),
 134 or
 135 .BR getgrnam (3).
 136 (Do not pass the returned pointer to
 137 .BR free (3).)
 138 .SH ERRORS
 139 .TP
 140 .B EAGAIN
 141 The service was temporarily unavailable; try again later.
 142 For NSS backends in glibc this indicates a temporary error talking to the backend.
 143 The error may correct itself, retrying later is suggested.
 144 .TP
 145 .B EINTR
 146 A signal was caught; see
 147 .BR signal (7).
 148 .TP
 149 .B EIO
 150 I/O error.
 151 .TP
 152 .B EMFILE
 153 The per-process limit on the number of open file descriptors has been reached.
 154 .TP
 155 .B ENFILE
 156 The system-wide limit on the total number of open files has been reached.
 157 .TP
 158 .\" not in POSIX
 159 .B ENOENT
 160 A necessary input file cannot be found.
 161 For NSS backends in glibc this indicates the backend is not correctly configured.
 162 .TP
 163 .B ENOMEM
 164 .\" not in POSIX
 165 Insufficient memory to allocate
 166 .I group
 167 structure.
 168 .TP
 169 .B ERANGE
 170 Insufficient buffer space supplied.
 171 .SH FILES
 172 .TP
 173 .I /etc/group
 174 local group database file
 175 .SH ATTRIBUTES
 176 For an explanation of the terms used in this section, see
 177 .BR attributes (7).
 178 .TS
 179 allbox;
 180 lbw11 lb lb
 181 l l l.
 182 Interface       Attribute       Value
 183 T{
 184 .BR getgrent ()
 185 T}      Thread safety   T{
 186 MT-Unsafe race:grent
 187 .br
 188 race:grentbuf locale
 189 T}
 190 T{
 191 .BR setgrent (),
 192 .BR endgrent ()
 193 T}      Thread safety   MT-Unsafe race:grent locale
 194 .TE
 195 .PP
 196 In the above table,
 197 .I grent
 198 in
 199 .I race:grent
 200 signifies that if any of the functions
 201 .BR setgrent (),
 202 .BR getgrent (),
 203 or
 204 .BR endgrent ()
 205 are used in parallel in different threads of a program,
 206 then data races could occur.
 207 .SH CONFORMING TO
 208 POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.
 209 .SH SEE ALSO
 210 .BR fgetgrent (3),
 211 .BR getgrent_r (3),
 212 .BR getgrgid (3),
 213 .BR getgrnam (3),
 214 .BR getgrouplist (3),
 215 .BR putgrent (3),
 216 .BR group (5)