man3/getgrnam.3

   1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
   2 .\"
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  12 .\" Since the Linux kernel and libraries are constantly changing, this
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  20 .\" Formatted or processed versions of this manual, if unaccompanied by
  21 .\" the source, must acknowledge the copyright and authors of this work.
  22 .\"
  23 .\" References consulted:
  24 .\"     Linux libc source code
  25 .\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
  26 .\"     386BSD man pages
  27 .\"
  28 .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
  29 .\" Modified 2003-11-15 by aeb
  30 .\"
  31 .TH GETGRNAM 3 2003-11-15 "" "Linux Programmer's Manual"
  32 .SH NAME
  33 getgrnam, getgrnam_r, getgrgid, getgrgid_r \- get group file entry
  34 .SH SYNOPSIS
  35 .nf
  36 .B #include <sys/types.h>
  37 .B #include <grp.h>
  38 .sp
  39 .BI "struct group *getgrnam(const char *" name );
  40 .sp
  41 .BI "struct group *getgrgid(gid_t " gid );
  42 .sp
  43 .BI "int getgrnam_r(const char *" name ", struct group *" gbuf ,
  44 .br
  45 .BI "          char *" buf ", size_t " buflen ", struct group **" gbufp );
  46 .sp
  47 .BI "int getgrgid_r(gid_t " gid ", struct group *" gbuf ,
  48 .br
  49 .BI "          char *" buf ", size_t " buflen ", struct group **" gbufp );
  50 .fi
  51 .SH DESCRIPTION
  52 The
  53 .BR getgrnam ()
  54 function returns a pointer to a structure containing
  55 the broken-out fields of the record in the group database
  56 (e.g., the local group file
  57 .IR /etc/group ,
  58 NIS, and LDAP)
  59 that matches the group name
  60 .IR name .
  61 .PP
  62 The
  63 .BR getgrgid ()
  64 function returns a pointer to a structure containing
  65 the broken-out fields of the record in the group database
  66 that matches the group ID
  67 .IR gid .
  68 .PP
  69 The
  70 .BR getgrnam_r ()
  71 and
  72 .BR getgrgid_r ()
  73 functions obtain the same information, but store the retrieved
  74 .I group
  75 structure
  76 in the space pointed to by
  77 .IR gbuf .
  78 This
  79 .I group
  80 structure contains pointers to strings, and these strings
  81 are stored in the buffer
  82 .I buf
  83 of size
  84 .IR buflen .
  85 A pointer to the result (in case of success) or NULL (in case no entry
  86 was found or an error occurred) is stored in
  87 .RI * gbufp .
  88 .PP
  89 The \fIgroup\fP structure is defined in \fI<grp.h>\fP as follows:
  90 .sp
  91 .RS +0.25i
  92 .nf
  93 struct group {
  94     char   *gr_name;       /* group name */
  95     char   *gr_passwd;     /* group password */
  96     gid_t   gr_gid;        /* group ID */
  97     char  **gr_mem;        /* group members */
  98 };
  99 .fi
 100 .RE
 101 .PP
 102 The maximum needed size for
 103 .I buf
 104 can be found using
 105 .BR sysconf (3)
 106 with the
 107 .B _SC_GETGR_R_SIZE_MAX
 108 parameter.
 109 .SH "RETURN VALUE"
 110 The
 111 .BR getgrnam ()
 112 and
 113 .BR getgrgid ()
 114 functions return a pointer to a
 115 .I group
 116 structure, or NULL if the matching entry
 117 is not found or an error occurs.
 118 If an error occurs,
 119 .I errno
 120 is set appropriately.
 121 If one wants to check
 122 .I errno
 123 after the call, it should be set to zero before the call.
 124 .LP
 125 The return value may point to static area, and may be overwritten
 126 by subsequent calls to
 127 .BR getgrent (3),
 128 .BR getgrgid (),
 129 or
 130 .BR getgrnam ().
 131 .LP
 132 The
 133 .BR getgrnam_r ()
 134 and
 135 .BR getgrgid_r ()
 136 functions return
 137 zero on success.
 138 In case of error, an error number is returned.
 139 .SH ERRORS
 140 .TP
 141 .BR 0 " or " ENOENT " or " ESRCH " or " EBADF " or " EPERM " or ... "
 142 The given
 143 .I name
 144 or
 145 .I gid
 146 was not found.
 147 .TP
 148 .B EINTR
 149 A signal was caught.
 150 .TP
 151 .B EIO
 152 I/O error.
 153 .TP
 154 .B EMFILE
 155 The maximum number
 156 .RB ( OPEN_MAX )
 157 of files was open already in the calling process.
 158 .TP
 159 .B ENFILE
 160 The maximum number of files was open already in the system.
 161 .TP
 162 .B ENOMEM
 163 .\" not in POSIX
 164 Insufficient memory to allocate group structure.
 165 .\" to allocate the group structure, or to allocate buffers
 166 .TP
 167 .B ERANGE
 168 Insufficient buffer space supplied.
 169 .SH FILES
 170 .TP
 171 .I /etc/group
 172 local group database file
 173 .SH "CONFORMING TO"
 174 SVr4, 4.3BSD, POSIX.1-2001
 175 .SH NOTES
 176 The formulation given above under "RETURN VALUE" is from POSIX.1-2001.
 177 It does not call "not found" an error, hence does not specify what value
 178 .I errno
 179 might have in this situation.
 180 But that makes it impossible to recognize
 181 errors.
 182 One might argue that according to POSIX
 183 .I errno
 184 should be left unchanged if an entry is not found.
 185 Experiments on various
 186 Unix-like systems shows that lots of different values occur in this
 187 situation: 0, ENOENT, EBADF, ESRCH, EWOULDBLOCK, EPERM and probably others.
 188 .\" more precisely:
 189 .\" AIX 5.1 - gives ESRCH
 190 .\" OSF1 4.0g - gives EWOULDBLOCK
 191 .\" libc, glibc, Irix 6.5 - give ENOENT
 192 .\" FreeBSD 4.8, OpenBSD 3.2, NetBSD 1.6 - give EPERM
 193 .\" SunOS 5.8 - gives EBADF
 194 .\" Tru64 5.1b, HP-UX-11i, SunOS 5.7 - give 0
 195 .SH "SEE ALSO"
 196 .BR endgrent (3),
 197 .BR fgetgrent (3),
 198 .BR getgrent (3),
 199 .BR getpwnam (3),
 200 .BR setgrent (3),
 201 .BR group (5)