1.\" Copyright (c) 1983, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)setuid.2 8.1 (Berkeley) 6/4/93 29.\" $FreeBSD: src/lib/libc/sys/setuid.2,v 1.13.2.7 2003/02/14 00:49:42 keramida Exp $ 30.\" 31.Dd June 4, 1993 32.Dt SETUID 2 33.Os 34.Sh NAME 35.Nm setuid , 36.Nm seteuid , 37.Nm setgid , 38.Nm setegid 39.Nd set user and group ID 40.Sh LIBRARY 41.Lb libc 42.Sh SYNOPSIS 43.In sys/types.h 44.In unistd.h 45.Ft int 46.Fn setuid "uid_t uid" 47.Ft int 48.Fn seteuid "uid_t euid" 49.Ft int 50.Fn setgid "gid_t gid" 51.Ft int 52.Fn setegid "gid_t egid" 53.Sh DESCRIPTION 54The 55.Fn setuid 56function 57sets the real and effective 58user IDs and the saved set-user-ID of the current process 59to the specified value. 60.\" Comment out next block for !_POSIX_SAVED_IDS 61.\" The real user ID and the saved set-user-ID are changed only if the 62.\" effective user ID is that of the super user. 63.\" I.e. 64.\" .Fn setuid 65.\" function is equal to 66.\" .Fn seteuid 67.\" function if the effective user ID is not that of the super user. 68.\" End of block 69The 70.Fn setuid 71function is permitted if the specified ID is equal to the real user ID 72.\" Comment out next line for !_POSIX_SAVED_IDS 73.\" or the saved set-user-ID 74.\" Next line is for Appendix B.4.2.2 case. 75or the effective user ID 76of the process, or if the effective user ID is that of the super user. 77.Pp 78The 79.Fn setgid 80function 81sets the real and effective 82group IDs and the saved set-group-ID of the current process 83to the specified value. 84.\" Comment out next block for !_POSIX_SAVED_IDS 85.\" The real group ID and the saved set-group-ID are changed only if the 86.\" effective user ID is that of the super user. 87.\" I.e. 88.\" .Fn setgid 89.\" function is equal to 90.\" .Fn setegid 91.\" function if the effective user ID is not that of the super user. 92.\" End of block 93The 94.Fn setgid 95function is permitted if the specified ID is equal to the real group ID 96.\" Comment out next line for !_POSIX_SAVED_IDS 97.\" or the saved set-group-ID 98.\" Next line is for Appendix B.4.2.2 case. 99or the effective group ID 100of the process, or if the effective user ID is that of the super user. 101.Pp 102The 103.Fn seteuid 104function 105.Pq Fn setegid 106sets the effective user ID (group ID) of the 107current process. 108The effective user ID may be set to the value 109of the real user ID or the saved set-user-ID (see 110.Xr intro 2 111and 112.Xr execve 2 ) ; 113in this way, the effective user ID of a set-user-ID executable 114may be toggled by switching to the real user ID, then re-enabled 115by reverting to the set-user-ID value. 116Similarly, the effective group ID may be set to the value 117of the real group ID or the saved set-group-ID. 118.Sh RETURN VALUES 119.Rv -std 120.Sh ERRORS 121The functions will fail if: 122.Bl -tag -width Er 123.It Bq Er EPERM 124The user is not the super user and the ID 125specified is not the real, effective ID, or saved ID. 126.El 127.Sh SEE ALSO 128.Xr getgid 2 , 129.Xr getuid 2 , 130.Xr issetugid 2 , 131.Xr setregid 2 , 132.Xr setreuid 2 133.Sh STANDARDS 134The 135.Fn setuid 136and 137.Fn setgid 138functions are compliant with the 139.St -p1003.1-90 140specification with 141.Dv _POSIX_SAVED_IDS 142.\" Uncomment next line for !_POSIX_SAVED_IDS 143not 144defined with the permitted extensions from Appendix B.4.2.2. 145The 146.Fn seteuid 147and 148.Fn setegid 149functions are extensions based on the 150.Tn POSIX 151concept of 152.Dv _POSIX_SAVED_IDS , 153and have been proposed for a future revision of the standard. 154.Sh HISTORY 155A 156.Fn setuid 157and a 158.Fn setgid 159function calls appeared in 160.At v7 . 161