xref: /dragonfly/lib/libc/gen/getgrent.3 (revision 8a7bdfea) 
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32.\"     From: @(#)getgrent.3	8.2 (Berkeley) 4/19/94
33.\" $FreeBSD: src/lib/libc/gen/getgrent.3,v 1.12.2.4 2003/03/15 15:11:05 trhodes Exp $
34.\" $DragonFly: src/lib/libc/gen/getgrent.3,v 1.5 2008/04/19 10:08:05 swildner Exp $
35.\"
36.Dd April 19, 2008
37.Dt GETGRENT 3
38.Os
39.Sh NAME
40.Nm getgrent ,
41.Nm getgrnam ,
42.Nm getgrgid ,
43.Nm setgroupent ,
44.Nm setgrent ,
45.Nm endgrent
46.Nd group database operations
47.Sh LIBRARY
48.Lb libc
49.Sh SYNOPSIS
50.In sys/types.h
51.In grp.h
52.Ft struct group *
53.Fn getgrent void
54.Ft struct group *
55.Fn getgrnam "const char *name"
56.Ft struct group *
57.Fn getgrgid "gid_t gid"
58.Ft int
59.Fn setgroupent "int stayopen"
60.Ft int
61.Fn setgrent void
62.Ft void
63.Fn endgrent void
64.Sh DESCRIPTION
65These functions operate on the group database file
66.Pa /etc/group
67which is described
68in
69.Xr group 5 .
70Each line of the database is defined by the structure
71.Vt group
72found in the include
73file
74.In grp.h :
75.Bd -literal -offset indent
76struct group {
77	char	*gr_name;	/* group name */
78	char	*gr_passwd;	/* group password */
79	int	gr_gid;		/* group id */
80	char	**gr_mem;	/* group members */
81};
82.Ed
83.Pp
84The functions
85.Fn getgrnam
86and
87.Fn getgrgid
88search the group database for the given group name pointed to by
89.Fa name
90or the group id pointed to by
91.Fa gid ,
92respectively, returning the first one encountered.  Identical group
93names or group gids may result in undefined behavior.
94.Pp
95The
96.Fn getgrent
97function
98sequentially reads the group database and is intended for programs
99that wish to step through the complete list of groups.
100.Pp
101All three routines will open the group file for reading, if necessary.
102.Pp
103The
104.Fn setgroupent
105function
106opens the file, or rewinds it if it is already open.  If
107.Fa stayopen
108is non-zero, file descriptors are left open, significantly speeding
109functions subsequent calls.  This functionality is unnecessary for
110.Fn getgrent
111as it doesn't close its file descriptors by default.  It should also
112be noted that it is dangerous for long-running programs to use this
113functionality as the group file may be updated.
114.Pp
115The
116.Fn setgrent
117function
118is identical to
119.Fn setgroupent
120with an argument of zero.
121.Pp
122The
123.Fn endgrent
124function
125closes any open files.
126.Sh YP/NIS INTERACTION
127When the
128.Xr yp 8
129group database is enabled, the
130.Fn getgrnam
131and
132.Fn getgrgid
133functions use the YP maps
134.Dq Li group.byname
135and
136.Dq Li group.bygid ,
137respectively, if the requested group is not found in the local
138.Pa /etc/group
139file.  The
140.Fn getgrent
141function will step through the YP map
142.Dq Li group.byname
143if the entire map is enabled as described in
144.Xr group 5 .
145.Sh RETURN VALUES
146The functions
147.Fn getgrent ,
148.Fn getgrnam ,
149and
150.Fn getgrgid ,
151return a pointer to the group entry if successful; if end-of-file
152is reached or an error occurs a null pointer is returned.
153The functions
154.Fn setgroupent
155and
156.Fn setgrent
157return the value 1 if successful, otherwise the value
1580 is returned.
159The
160.Fn endgrent
161function has no return value.
162.Sh FILES
163.Bl -tag -width /etc/group -compact
164.It Pa /etc/group
165group database file
166.El
167.Sh COMPATIBILITY
168The historic function
169.Fn setgrfile ,
170which allowed the specification of alternate password databases, has
171been deprecated and is no longer available.
172.Sh SEE ALSO
173.Xr getpwent 3 ,
174.Xr group 5 ,
175.Xr yp 8
176.Sh HISTORY
177The functions
178.Fn endgrent ,
179.Fn getgrent ,
180.Fn getgrnam ,
181.Fn getgrgid ,
182and
183.Fn setgrent
184appeared in
185.At v7 .
186The functions
187.Fn setgrfile
188and
189.Fn setgroupent
190appeared in
191.Bx 4.3 Reno .
192.Sh BUGS
193The functions
194.Fn getgrent ,
195.Fn getgrnam ,
196.Fn getgrgid ,
197.Fn setgroupent
198and
199.Fn setgrent
200leave their results in an internal static object and return
201a pointer to that object.
202Subsequent calls to
203the same function
204will modify the same object.
205