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30 .\" @(#)getgrent.3 8.2 (Berkeley) 4/19/94
31 .\"
32 .Dd April 30, 2008
33 .Dt GETGRENT 3
34 .Os
35 .Sh NAME
36 .Nm getgrent ,
37 .Nm getgrent_r ,
38 .Nm getgrgid ,
39 .Nm getgrgid_r ,
40 .Nm getgrnam ,
41 .Nm getgrnam_r ,
42 .Nm setgroupent ,
43 .\" .Nm setgrfile ,
44 .Nm setgrent ,
45 .Nm endgrent
46 .Nd group database operations
47 .Sh LIBRARY
48 .Lb libc
49 .Sh SYNOPSIS
50 .In grp.h
51 .Ft struct group *
52 .Fn getgrent void
53 .Ft int
54 .Fo getgrent_r
55 .Fa "struct group *grp"
56 .Fa "char *buffer"
57 .Fa "size_t buflen"
58 .Fa "struct group **result"
59 .Fc
60 .Ft struct group *
61 .Fn getgrgid "gid_t gid"
62 .Ft int
63 .Fo getgrgid_r
64 .Fa "gid_t gid"
65 .Fa "struct group *grp"
66 .Fa "char *buffer"
67 .Fa "size_t buflen"
68 .Fa "struct group **result"
69 .Fc
70 .Ft struct group *
71 .Fn getgrnam "const char *name"
72 .Ft int
73 .Fo getgrnam_r
74 .Fa "const char *name"
75 .Fa "struct group *grp"
76 .Fa "char *buffer"
77 .Fa "size_t buflen"
78 .Fa "struct group **result"
79 .Fc
80 .Ft int
81 .Fn setgroupent "int stayopen"
82 .\" .Ft void
83 .\" .Fn setgrfile "const char *name"
84 .Ft void
85 .Fn setgrent void
86 .Ft void
87 .Fn endgrent void
88 .Sh DESCRIPTION
89 These functions operate on the group database which is described in
90 .Xr group 5 .
91 Each line of the database is defined by the structure
92 .Ar group
93 found in the include
94 file
95 .In grp.h :
96 .Bd -literal -offset indent
97 struct group {
98 char *gr_name; /* group name */
99 char *gr_passwd; /* group password */
100 gid_t gr_gid; /* group id */
101 char **gr_mem; /* group members */
102 };
103 .Ed
104 .Pp
105 The functions
106 .Fn getgrnam
107 and
108 .Fn getgrgid
109 search the group database for the given group name pointed to by
110 .Ar name
111 or the group id pointed to by
112 .Ar gid ,
113 respectively, returning the first one encountered.
114 Identical group names or group ids may result in undefined behavior.
115 .Pp
116 The
117 .Fn getgrent
118 function sequentially reads the group database and is intended for programs
119 that wish to step through the complete list of groups.
120 .Pp
121 All three functions will open the group file for reading, if necessary.
122 .Pp
123 The functions
124 .Fn getgrnam_r ,
125 .Fn getgrgid_r ,
126 and
127 .Fn getgrent_r
128 act like their non re-entrant counterparts
129 respectively, updating the contents of
130 .Ar grp
131 and storing a pointer to that in
132 .Ar result ,
133 and returning
134 .Dv 0 .
135 Storage used by
136 .Ar grp
137 is allocated from
138 .Ar buffer ,
139 which is
140 .Ar buflen
141 bytes in size.
142 If the requested entry cannot be found,
143 .Ar result
144 will point to
145 .Dv NULL
146 and
147 .Dv 0
148 will be returned.
149 If an error occurs,
150 a non-zero error number will be returned and
151 .Ar result
152 will point to
153 .Dv NULL .
154 Calling
155 .Fn getgrent_r
156 from multiple threads will result in each thread reading a disjoint portion
157 of the group database.
158 .Pp
159 The
160 .Fn setgroupent
161 function opens the file, or rewinds it if it is already open.
162 If
163 .Fa stayopen
164 is non-zero, file descriptors are left open, significantly speeding
165 functions subsequent calls.
166 This functionality is unnecessary for
167 .Fn getgrent
168 as it doesn't close its file descriptors by default.
169 It should also be noted that it is dangerous for long-running
170 programs to use this functionality as the group file may be updated.
171 .Pp
172 The
173 .Fn setgrent
174 function is equivalent to
175 .Fn setgroupent
176 with an argument of zero.
177 .Pp
178 The
179 .Fn endgrent
180 function closes any open files.
181 .Sh RETURN VALUES
182 The functions
183 .Fn getgrgid ,
184 .Fn getgrnam ,
185 and
186 .Fn getgrent
187 return a valid pointer to a group structure on success
188 and a
189 .Dv NULL
190 pointer if the entry was not found or an error occured.
191 If an error occured, the global variable
192 .Dv errno
193 is set to indicate the nature of the failure.
194 .Pp
195 The functions
196 .Fn getgrgid_r ,
197 .Fn getgrnam_r ,
198 and
199 .Fn getgrent_r
200 return
201 .Dv 0
202 on success or entry not found, and non-zero on failure, setting the global
203 variable
204 .Dv errno
205 to indicate the nature of the failure.
206 .Pp
207 The
208 .Fn setgroupent
209 function returns the value 1 if successful, otherwise the value
210 0 is returned, setting the global variable
211 .Dv errno
212 to indicate the nature of the failure.
213 .Pp
214 The
215 .Fn endgrent
216 and
217 .Fn setgrent
218 functions have no return value.
219 .Sh ERRORS
220 The following error codes may be set in
221 .Va errno
222 for
223 .Nm getgrent ,
224 .Nm getgrent_r ,
225 .Nm getgrnam ,
226 .Nm getgrnam_r ,
227 .Nm getgrgid ,
228 .Nm getgrgid_r ,
229 and
230 .Nm setgroupent :
231 .Bl -tag -width Er
232 .It Bq Er EIO
233 An I/O error has occurred.
234 .It Bq Er EINTR
235 A signal was caught during the database search.
236 .It Bq Er EMFILE
237 The limit on open files for this process has been reached.
238 .It Bq Er ENFILE
239 The system limit on open files has been reached.
240 .El
241 .Pp
242 The following error code may be set in
243 .Va errno
244 for
245 .Nm getgrent_r ,
246 .Nm getgrnam_r ,
247 and
248 .Nm getgrgid_r :
249 .Bl -tag -width Er
250 .It Bq Er ERANGE
251 The resulting
252 .Ft struct group
253 does not fit in the space defined by
254 .Dv buffer
255 and
256 .Dv buflen
257 .El
258 .Pp
259 Other
260 .Dv errno
261 values may be set depending on the specific database backends.
262 .Sh FILES
263 .Bl -tag -width /etc/group -compact
264 .It Pa /etc/group
265 group database file
266 .El
267 .Sh SEE ALSO
268 .Xr getpwent 3 ,
269 .Xr group 5 ,
270 .Xr nsswitch.conf 5
271 .Sh STANDARDS
272 The
273 .Fn getgrgid
274 and
275 .Fn getgrnam
276 functions conform to
277 .St -p1003.1-90 .
278 The
279 .Fn getgrgid_r
280 and
281 .Fn getgrnam_r
282 functions conform to
283 .St -p1003.1c-95 .
284 The
285 .Fn endgrent ,
286 .Fn getgrent ,
287 and
288 .Fn setgrent
289 functions conform to
290 .St -xpg4.2
291 and
292 .St -p1003.1-2004
293 (XSI extension).
294 .Sh HISTORY
295 The functions
296 .Fn endgrent ,
297 .Fn getgrent ,
298 .Fn getgrgid ,
299 .Fn getgrnam ,
300 and
301 .Fn setgrent
302 appeared in
303 .At v7 .
304 The functions
305 .Fn setgrfile
306 and
307 .Fn setgroupent
308 appeared in
309 .Bx 4.3 Reno .
310 The functions
311 .Fn getgrgid_r
312 and
313 .Fn getgrnam_r
314 appeared in
315 .Nx 3.0 .
316 .Sh COMPATIBILITY
317 The historic function
318 .Fn setgrfile ,
319 which allowed the specification of alternative group databases, has
320 been deprecated and is no longer available.
321 .Sh BUGS
322 The functions
323 .Fn getgrent ,
324 .Fn getgrgid ,
325 .Fn getgrnam ,
326 .Fn setgroupent
327 and
328 .Fn setgrent
329 leave their results in an internal static object and return
330 a pointer to that object.
331 Subsequent calls to the same function will modify the same object.
332 .Pp
333 The functions
334 .Fn getgrent ,
335 .Fn endgrent ,
336 .Fn setgroupent ,
337 and
338 .Fn setgrent
339 are fairly useless in a networked environment and should be
340 avoided, if possible.
341 .Fn getgrent
342 makes no attempt to suppress duplicate information if multiple
343 sources are specified in
344 .Xr nsswitch.conf 5