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32 .\" @(#)setuid.2 8.1 (Berkeley) 6/4/93
33 .\" $FreeBSD: src/lib/libc/sys/setuid.2,v 1.13.2.7 2003/02/14 00:49:42 keramida Exp $
34 .\" $DragonFly: src/lib/libc/sys/setuid.2,v 1.2 2003/06/17 04:26:47 dillon Exp $
35 .\"
36 .Dd June 4, 1993
37 .Dt SETUID 2
38 .Os
39 .Sh NAME
40 .Nm setuid ,
41 .Nm seteuid ,
42 .Nm setgid ,
43 .Nm setegid ,
44 .Nd set user and group ID
45 .Sh LIBRARY
46 .Lb libc
47 .Sh SYNOPSIS
48 .In sys/types.h
49 .In unistd.h
50 .Ft int
51 .Fn setuid "uid_t uid"
52 .Ft int
53 .Fn seteuid "uid_t euid"
54 .Ft int
55 .Fn setgid "gid_t gid"
56 .Ft int
57 .Fn setegid "gid_t egid"
58 .Sh DESCRIPTION
59 The
60 .Fn setuid
61 function
62 sets the real and effective
63 user IDs and the saved set-user-ID of the current process
64 to the specified value.
65 .\" Comment out next block for !_POSIX_SAVED_IDS
66 .\" The real user ID and the saved set-user-ID are changed only if the
67 .\" effective user ID is that of the super user.
68 .\" I.e.
69 .\" .Fn setuid
70 .\" function is equal to
71 .\" .Fn seteuid
72 .\" function if the effective user ID is not that of the super user.
73 .\" End of block
74 The
75 .Fn setuid
76 function is permitted if the specified ID is equal to the real user ID
77 .\" Comment out next line for !_POSIX_SAVED_IDS
78 .\" or the saved set-user-ID
79 .\" Next line is for Appendix B.4.2.2 case.
80 or the effective user ID
81 of the process, or if the effective user ID is that of the super user.
82 .Pp
83 The
84 .Fn setgid
85 function
86 sets the real and effective
87 group IDs and the saved set-group-ID of the current process
88 to the specified value.
89 .\" Comment out next block for !_POSIX_SAVED_IDS
90 .\" The real group ID and the saved set-group-ID are changed only if the
91 .\" effective user ID is that of the super user.
92 .\" I.e.
93 .\" .Fn setgid
94 .\" function is equal to
95 .\" .Fn setegid
96 .\" function if the effective user ID is not that of the super user.
97 .\" End of block
98 The
99 .Fn setgid
100 function is permitted if the specified ID is equal to the real group ID
101 .\" Comment out next line for !_POSIX_SAVED_IDS
102 .\" or the saved set-group-ID
103 .\" Next line is for Appendix B.4.2.2 case.
104 or the effective group ID
105 of the process, or if the effective user ID is that of the super user.
106 .Pp
107 The
108 .Fn seteuid
109 function
110 .Pq Fn setegid
111 sets the effective user ID (group ID) of the
112 current process.
113 The effective user ID may be set to the value
114 of the real user ID or the saved set-user-ID (see
115 .Xr intro 2
116 and
117 .Xr execve 2 ) ;
118 in this way, the effective user ID of a set-user-ID executable
119 may be toggled by switching to the real user ID, then re-enabled
120 by reverting to the set-user-ID value.
121 Similarly, the effective group ID may be set to the value
122 of the real group ID or the saved set-group-ID.
123 .Sh RETURN VALUES
124 .Rv -std
125 .Sh ERRORS
126 The functions will fail if:
127 .Bl -tag -width Er
128 .It Bq Er EPERM
129 The user is not the super user and the ID
130 specified is not the real, effective ID, or saved ID.
131 .El
132 .Sh SEE ALSO
133 .Xr getgid 2 ,
134 .Xr getuid 2 ,
135 .Xr issetugid 2 ,
136 .Xr setregid 2 ,
137 .Xr setreuid 2
138 .Sh STANDARDS
139 The
140 .Fn setuid
141 and
142 .Fn setgid
143 functions are compliant with the
144 .St -p1003.1-90
145 specification with
146 .Li _POSIX_SAVED_IDS
147 .\" Uncomment next line for !_POSIX_SAVED_IDS
148 not
149 defined with the permitted extensions from Appendix B.4.2.2.
150 The
151 .Fn seteuid
152 and
153 .Fn setegid
154 functions are extensions based on the
155 .Tn POSIX
156 concept of
157 .Li _POSIX_SAVED_IDS ,
158 and have been proposed for a future revision of the standard.
159 .Sh HISTORY
160 A
161 .Fn setuid
162 and a
163 .Fn setgid
164 function calls appeared in
165 .At v7 .