man3/getgrnam.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 .\"
  30 .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
  31 .\" Modified 2003-11-15 by aeb
  32 .\"
  33 .TH GETGRNAM 3 2017-09-15 "" "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 .PP
  41 .BI "struct group *getgrnam(const char *" name );
  42 .PP
  43 .BI "struct group *getgrgid(gid_t " gid );
  44 .PP
  45 .BI "int getgrnam_r(const char *" name ", struct group *" grp ,
  46 .BI "          char *" buf ", size_t " buflen ", struct group **" result );
  47 .PP
  48 .BI "int getgrgid_r(gid_t " gid ", struct group *" grp ,
  49 .BI "          char *" buf ", size_t " buflen ", struct group **" result );
  50 .fi
  51 .PP
  52 .in -4n
  53 Feature Test Macro Requirements for glibc (see
  54 .BR feature_test_macros (7)):
  55 .ad l
  56 .in
  57 .PP
  58 .BR getgrnam_r (),
  59 .BR getgrgid_r ():
  60 .RS 4
  61 _POSIX_C_SOURCE
  62     || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
  63 .RE
  64 .ad b
  65 .SH DESCRIPTION
  66 The
  67 .BR getgrnam ()
  68 function returns a pointer to a structure containing
  69 the broken-out fields of the record in the group database
  70 (e.g., the local group file
  71 .IR /etc/group ,
  72 NIS, and LDAP)
  73 that matches the group name
  74 .IR name .
  75 .PP
  76 The
  77 .BR getgrgid ()
  78 function returns a pointer to a structure containing
  79 the broken-out fields of the record in the group database
  80 that matches the group ID
  81 .IR gid .
  82 .PP
  83 The \fIgroup\fP structure is defined in \fI<grp.h>\fP as follows:
  84 .PP
  85 .in +4n
  86 .EX
  87 struct group {
  88     char   *gr_name;        /* group name */
  89     char   *gr_passwd;      /* group password */
  90     gid_t   gr_gid;         /* group ID */
  91     char  **gr_mem;         /* NULL-terminated array of pointers
  92                                to names of group members */
  93 };
  94 .EE
  95 .in
  96 .PP
  97 For more information about the fields of this structure, see
  98 .BR group (5).
  99 .PP
 100 The
 101 .BR getgrnam_r ()
 102 and
 103 .BR getgrgid_r ()
 104 functions obtain the same information as
 105 .BR getgrnam ()
 106 and
 107 .BR getgrgid (),
 108 but store the retrieved
 109 .I group
 110 structure
 111 in the space pointed to by
 112 .IR grp .
 113 The string fields pointed to by the members of the
 114 .I group
 115 structure are stored in the buffer
 116 .I buf
 117 of size
 118 .IR buflen .
 119 A pointer to the result (in case of success) or NULL (in case no entry
 120 was found or an error occurred) is stored in
 121 .IR *result .
 122 .PP
 123 The call
 124 .PP
 125     sysconf(_SC_GETGR_R_SIZE_MAX)
 126 .PP
 127 returns either \-1, without changing
 128 .IR errno ,
 129 or an initial suggested size for
 130 .IR buf .
 131 (If this size is too small,
 132 the call fails with
 133 .BR ERANGE ,
 134 in which case the caller can retry with a larger buffer.)
 135 .SH RETURN VALUE
 136 The
 137 .BR getgrnam ()
 138 and
 139 .BR getgrgid ()
 140 functions return a pointer to a
 141 .I group
 142 structure, or NULL if the matching entry
 143 is not found or an error occurs.
 144 If an error occurs,
 145 .I errno
 146 is set appropriately.
 147 If one wants to check
 148 .I errno
 149 after the call, it should be set to zero before the call.
 150 .PP
 151 The return value may point to a static area, and may be overwritten
 152 by subsequent calls to
 153 .BR getgrent (3),
 154 .BR getgrgid (),
 155 or
 156 .BR getgrnam ().
 157 (Do not pass the returned pointer to
 158 .BR free (3).)
 159 .PP
 160 On success,
 161 .BR getgrnam_r ()
 162 and
 163 .BR getgrgid_r ()
 164 return zero, and set
 165 .IR *result
 166 to
 167 .IR grp .
 168 If no matching group record was found,
 169 these functions return 0 and store NULL in
 170 .IR *result .
 171 In case of error, an error number is returned, and NULL is stored in
 172 .IR *result .
 173 .SH ERRORS
 174 .TP
 175 .BR 0 " or " ENOENT " or " ESRCH " or " EBADF " or " EPERM " or ... "
 176 The given
 177 .I name
 178 or
 179 .I gid
 180 was not found.
 181 .TP
 182 .B EINTR
 183 A signal was caught; see
 184 .BR signal (7).
 185 .TP
 186 .B EIO
 187 I/O error.
 188 .TP
 189 .B EMFILE
 190 The per-process limit on the number of open file descriptors has been reached.
 191 .TP
 192 .B ENFILE
 193 The system-wide limit on the total number of open files has been reached.
 194 .TP
 195 .B ENOMEM
 196 .\" not in POSIX
 197 Insufficient memory to allocate
 198 .I group
 199 structure.
 200 .\" to allocate the group structure, or to allocate buffers
 201 .TP
 202 .B ERANGE
 203 Insufficient buffer space supplied.
 204 .SH FILES
 205 .TP
 206 .I /etc/group
 207 local group database file
 208 .SH ATTRIBUTES
 209 For an explanation of the terms used in this section, see
 210 .BR attributes (7).
 211 .TS
 212 allbox;
 213 lb lb lb
 214 l l l.
 215 Interface       Attribute       Value
 216 T{
 217 .BR getgrnam ()
 218 T}      Thread safety   MT-Unsafe race:grnam locale
 219 T{
 220 .BR getgrgid ()
 221 T}      Thread safety   MT-Unsafe race:grgid locale
 222 T{
 223 .BR getgrnam_r (),
 224 .br
 225 .BR getgrgid_r ()
 226 T}      Thread safety   MT-Safe locale
 227 .TE
 228 .SH CONFORMING TO
 229 POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.
 230 .SH NOTES
 231 The formulation given above under "RETURN VALUE" is from POSIX.1.
 232 .\" POSIX.1-2001, POSIX.1-2008
 233 It does not call "not found" an error, hence does not specify what value
 234 .I errno
 235 might have in this situation.
 236 But that makes it impossible to recognize
 237 errors.
 238 One might argue that according to POSIX
 239 .I errno
 240 should be left unchanged if an entry is not found.
 241 Experiments on various
 242 UNIX-like systems show that lots of different values occur in this
 243 situation: 0, ENOENT, EBADF, ESRCH, EWOULDBLOCK, EPERM, and probably others.
 244 .\" more precisely:
 245 .\" AIX 5.1 - gives ESRCH
 246 .\" OSF1 4.0g - gives EWOULDBLOCK
 247 .\" libc, glibc up to version 2.6, Irix 6.5 - give ENOENT
 248 .\" glibc since version 2.7 - give 0
 249 .\" FreeBSD 4.8, OpenBSD 3.2, NetBSD 1.6 - give EPERM
 250 .\" SunOS 5.8 - gives EBADF
 251 .\" Tru64 5.1b, HP-UX-11i, SunOS 5.7 - give 0
 252 .SH SEE ALSO
 253 .BR endgrent (3),
 254 .BR fgetgrent (3),
 255 .BR getgrent (3),
 256 .BR getpwnam (3),
 257 .BR setgrent (3),
 258 .BR group (5)