man3/getgrnam.3

   1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
   2 .\"
   3 .\" %%%LICENSE_START(VERBATIM)
   4 .\" Permission is granted to make and distribute verbatim copies of this
   5 .\" manual provided the copyright notice and this permission notice are
   6 .\" preserved on all copies.
   7 .\"
   8 .\" Permission is granted to copy and distribute modified versions of this
   9 .\" manual under the conditions for verbatim copying, provided that the
  10 .\" entire resulting derived work is distributed under the terms of a
  11 .\" permission notice identical to this one.
  12 .\"
  13 .\" Since the Linux kernel and libraries are constantly changing, this
  14 .\" manual page may be incorrect or out-of-date.  The author(s) assume no
  15 .\" responsibility for errors or omissions, or for damages resulting from
  16 .\" the use of the information contained herein.  The author(s) may not
  17 .\" have taken the same level of care in the production of this manual,
  18 .\" which is licensed free of charge, as they might when working
  19 .\" professionally.
  20 .\"
  21 .\" Formatted or processed versions of this manual, if unaccompanied by
  22 .\" the source, must acknowledge the copyright and authors of this work.
  23 .\" %%%LICENSE_END
  24 .\"
  25 .\" References consulted:
  26 .\"     Linux libc source code
  27 .\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
  28 .\"     386BSD man pages
  29 .\"
  30 .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
  31 .\" Modified 2003-11-15 by aeb
  32 .\"
  33 .TH GETGRNAM 3 2016-03-15 "" "Linux Programmer's Manual"
  34 .SH NAME
  35 getgrnam, getgrnam_r, getgrgid, getgrgid_r \- get group file entry
  36 .SH SYNOPSIS
  37 .nf
  38 .B #include <sys/types.h>
  39 .B #include <grp.h>
  40 .sp
  41 .BI "struct group *getgrnam(const char *" name );
  42 .sp
  43 .BI "struct group *getgrgid(gid_t " gid );
  44 .sp
  45 .BI "int getgrnam_r(const char *" name ", struct group *" grp ,
  46 .br
  47 .BI "          char *" buf ", size_t " buflen ", struct group **" result );
  48 .sp
  49 .BI "int getgrgid_r(gid_t " gid ", struct group *" grp ,
  50 .br
  51 .BI "          char *" buf ", size_t " buflen ", struct group **" result );
  52 .fi
  53 .sp
  54 .in -4n
  55 Feature Test Macro Requirements for glibc (see
  56 .BR feature_test_macros (7)):
  57 .ad l
  58 .in
  59 .sp
  60 .BR getgrnam_r (),
  61 .BR getgrgid_r ():
  62 .RS 4
  63 _POSIX_C_SOURCE
  64     || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
  65 .RE
  66 .ad b
  67 .SH DESCRIPTION
  68 The
  69 .BR getgrnam ()
  70 function returns a pointer to a structure containing
  71 the broken-out fields of the record in the group database
  72 (e.g., the local group file
  73 .IR /etc/group ,
  74 NIS, and LDAP)
  75 that matches the group name
  76 .IR name .
  77 .PP
  78 The
  79 .BR getgrgid ()
  80 function returns a pointer to a structure containing
  81 the broken-out fields of the record in the group database
  82 that matches the group ID
  83 .IR gid .
  84 .PP
  85 The \fIgroup\fP structure is defined in \fI<grp.h>\fP as follows:
  86 .sp
  87 .in +4n
  88 .nf
  89 struct group {
  90     char   *gr_name;        /* group name */
  91     char   *gr_passwd;      /* group password */
  92     gid_t   gr_gid;         /* group ID */
  93     char  **gr_mem;         /* NULL-terminated array of pointers
  94                                to names of group members */
  95 };
  96 .fi
  97 .in
  98 .PP
  99 For more information about the fields of this structure, see
 100 .BR group (5).
 101 .PP
 102 The
 103 .BR getgrnam_r ()
 104 and
 105 .BR getgrgid_r ()
 106 functions obtain the same information as
 107 .BR getgrnam ()
 108 and
 109 .BR getgrgid (),
 110 but store the retrieved
 111 .I group
 112 structure
 113 in the space pointed to by
 114 .IR grp .
 115 The string fields pointed to by the members of the
 116 .I group
 117 structure are stored in the buffer
 118 .I buf
 119 of size
 120 .IR buflen .
 121 A pointer to the result (in case of success) or NULL (in case no entry
 122 was found or an error occurred) is stored in
 123 .IR *result .
 124 .PP
 125 The call
 126
 127     sysconf(_SC_GETGR_R_SIZE_MAX)
 128
 129 returns either \-1, without changing
 130 .IR errno ,
 131 or an initial suggested size for
 132 .IR buf .
 133 (If this size is too small,
 134 the call fails with
 135 .BR ERANGE ,
 136 in which case the caller can retry with a larger buffer.)
 137 .SH RETURN VALUE
 138 The
 139 .BR getgrnam ()
 140 and
 141 .BR getgrgid ()
 142 functions return a pointer to a
 143 .I group
 144 structure, or NULL if the matching entry
 145 is not found or an error occurs.
 146 If an error occurs,
 147 .I errno
 148 is set appropriately.
 149 If one wants to check
 150 .I errno
 151 after the call, it should be set to zero before the call.
 152 .LP
 153 The return value may point to a static area, and may be overwritten
 154 by subsequent calls to
 155 .BR getgrent (3),
 156 .BR getgrgid (),
 157 or
 158 .BR getgrnam ().
 159 (Do not pass the returned pointer to
 160 .BR free (3).)
 161 .LP
 162 On success,
 163 .BR getgrnam_r ()
 164 and
 165 .BR getgrgid_r ()
 166 return zero, and set
 167 .IR *result
 168 to
 169 .IR grp .
 170 If no matching group record was found,
 171 these functions return 0 and store NULL in
 172 .IR *result .
 173 In case of error, an error number is returned, and NULL is stored in
 174 .IR *result .
 175 .SH ERRORS
 176 .TP
 177 .BR 0 " or " ENOENT " or " ESRCH " or " EBADF " or " EPERM " or ... "
 178 The given
 179 .I name
 180 or
 181 .I gid
 182 was not found.
 183 .TP
 184 .B EINTR
 185 A signal was caught; see
 186 .BR signal (7).
 187 .TP
 188 .B EIO
 189 I/O error.
 190 .TP
 191 .B EMFILE
 192 The per-process limit on the number of open file descriptors has been reached.
 193 .TP
 194 .B ENFILE
 195 The system-wide limit on the total number of open files has been reached.
 196 .TP
 197 .B ENOMEM
 198 .\" not in POSIX
 199 Insufficient memory to allocate
 200 .I group
 201 structure.
 202 .\" to allocate the group structure, or to allocate buffers
 203 .TP
 204 .B ERANGE
 205 Insufficient buffer space supplied.
 206 .SH FILES
 207 .TP
 208 .I /etc/group
 209 local group database file
 210 .SH ATTRIBUTES
 211 For an explanation of the terms used in this section, see
 212 .BR attributes (7).
 213 .TS
 214 allbox;
 215 lb lb lb
 216 l l l.
 217 Interface       Attribute       Value
 218 T{
 219 .BR getgrnam ()
 220 T}      Thread safety   MT-Unsafe race:grnam locale
 221 T{
 222 .BR getgrgid ()
 223 T}      Thread safety   MT-Unsafe race:grgid locale
 224 T{
 225 .BR getgrnam_r (),
 226 .br
 227 .BR getgrgid_r ()
 228 T}      Thread safety   MT-Safe locale
 229 .TE
 230 .SH CONFORMING TO
 231 POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.
 232 .SH NOTES
 233 The formulation given above under "RETURN VALUE" is from POSIX.1.
 234 .\" POSIX.1-2001, POSIX.1-2008
 235 It does not call "not found" an error, hence does not specify what value
 236 .I errno
 237 might have in this situation.
 238 But that makes it impossible to recognize
 239 errors.
 240 One might argue that according to POSIX
 241 .I errno
 242 should be left unchanged if an entry is not found.
 243 Experiments on various
 244 UNIX-like systems show that lots of different values occur in this
 245 situation: 0, ENOENT, EBADF, ESRCH, EWOULDBLOCK, EPERM, and probably others.
 246 .\" more precisely:
 247 .\" AIX 5.1 - gives ESRCH
 248 .\" OSF1 4.0g - gives EWOULDBLOCK
 249 .\" libc, glibc up to version 2.6, Irix 6.5 - give ENOENT
 250 .\" glibc since version 2.7 - give 0
 251 .\" FreeBSD 4.8, OpenBSD 3.2, NetBSD 1.6 - give EPERM
 252 .\" SunOS 5.8 - gives EBADF
 253 .\" Tru64 5.1b, HP-UX-11i, SunOS 5.7 - give 0
 254 .SH SEE ALSO
 255 .BR endgrent (3),
 256 .BR fgetgrent (3),
 257 .BR getgrent (3),
 258 .BR getpwnam (3),
 259 .BR setgrent (3),
 260 .BR group (5)