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
  13 .\" manual page may be incorrect or out-of-date.  The author(s) assume no
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  15 .\" the use of the information contained herein.  The author(s) may not
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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 _SC_GETGR_R_SIZE_MAX parameter.
 107 .SH "RETURN VALUE"
 108 The \fBgetgrnam\fP() and \fBgetgrgid\fP() functions return a pointer to a
 109 .I group
 110 structure, or NULL if the matching entry
 111 is not found or an error occurs.
 112 If an error occurs,
 113 .I errno
 114 is set appropriately.
 115 If one wants to check
 116 .I errno
 117 after the call, it should be set to zero before the call.
 118 .LP
 119 The return value may point to static area, and may be overwritten
 120 by subsequent calls to
 121 .BR getgrent (),
 122 .BR getgrgid (),
 123 or
 124 .BR getgrnam ().
 125 .LP
 126 The  \fBgetgrnam_r\fP() and \fBgetgrgid_r\fP() functions return
 127 zero on success. In case of error, an error number is returned.
 128 .SH ERRORS
 129 .TP
 130 .BR 0 " or " ENOENT " or " ESRCH " or " EBADF " or " EPERM " or ... "
 131 The given
 132 .I name
 133 or
 134 .I gid
 135 was not found.
 136 .TP
 137 .B EINTR
 138 A signal was caught.
 139 .TP
 140 .B EIO
 141 I/O error.
 142 .TP
 143 .B EMFILE
 144 The maximum number (OPEN_MAX) of files was open already in the calling process.
 145 .TP
 146 .B ENFILE
 147 The maximum number of files was open already in the system.
 148 .TP
 149 .B ENOMEM
 150 .\" not in POSIX
 151 Insufficient memory to allocate group structure.
 152 .\" to allocate the group structure, or to allocate buffers
 153 .TP
 154 .B ERANGE
 155 Insufficient buffer space supplied.
 156 .SH FILES
 157 .TP
 158 .I /etc/group
 159 local group database file
 160 .SH "CONFORMING TO"
 161 SVID 3, 4.3BSD, POSIX 1003.1-2003
 162 .SH NOTES
 163 The formulation given above under "RETURN VALUE" is from POSIX 1003.1-2001.
 164 It does not call "not found" an error, hence does not specify what value
 165 .I errno
 166 might have in this situation. But that makes it impossible to recognize
 167 errors. One might argue that according to POSIX
 168 .I errno
 169 should be left unchanged if an entry is not found. Experiments on various
 170 Unix-like systems shows that lots of different values occur in this
 171 situation: 0, ENOENT, EBADF, ESRCH, EWOULDBLOCK, EPERM and probably others.
 172 .\" more precisely:
 173 .\" AIX 5.1 - gives ESRCH
 174 .\" OSF1 4.0g - gives EWOULDBLOCK
 175 .\" libc, glibc, Irix 6.5 - give ENOENT
 176 .\" FreeBSD 4.8, OpenBSD 3.2, NetBSD 1.6 - give EPERM
 177 .\" SunOS 5.8 - gives EBADF
 178 .\" Tru64 5.1b, HP-UX-11i, SunOS 5.7 - give 0
 179 .SH "SEE ALSO"
 180 .BR endgrent (3),
 181 .BR fgetgrent (3),
 182 .BR getgrent (3),
 183 .BR getpwnam (3),
 184 .BR setgrent (3),
 185 .BR group (5)