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.\" $DragonFly: src/lib/libc/sys/setuid.2,v 1.2 2003/06/17 04:26:47 dillon Exp $ 31.\" 32.Dd June 4, 1993 33.Dt SETUID 2 34.Os 35.Sh NAME 36.Nm setuid , 37.Nm seteuid , 38.Nm setgid , 39.Nm setegid , 40.Nd set user and group ID 41.Sh LIBRARY 42.Lb libc 43.Sh SYNOPSIS 44.In sys/types.h 45.In unistd.h 46.Ft int 47.Fn setuid "uid_t uid" 48.Ft int 49.Fn seteuid "uid_t euid" 50.Ft int 51.Fn setgid "gid_t gid" 52.Ft int 53.Fn setegid "gid_t egid" 54.Sh DESCRIPTION 55The 56.Fn setuid 57function 58sets the real and effective 59user IDs and the saved set-user-ID of the current process 60to the specified value. 61.\" Comment out next block for !_POSIX_SAVED_IDS 62.\" The real user ID and the saved set-user-ID are changed only if the 63.\" effective user ID is that of the super user. 64.\" I.e. 65.\" .Fn setuid 66.\" function is equal to 67.\" .Fn seteuid 68.\" function if the effective user ID is not that of the super user. 69.\" End of block 70The 71.Fn setuid 72function is permitted if the specified ID is equal to the real user ID 73.\" Comment out next line for !_POSIX_SAVED_IDS 74.\" or the saved set-user-ID 75.\" Next line is for Appendix B.4.2.2 case. 76or the effective user ID 77of the process, or if the effective user ID is that of the super user. 78.Pp 79The 80.Fn setgid 81function 82sets the real and effective 83group IDs and the saved set-group-ID of the current process 84to the specified value. 85.\" Comment out next block for !_POSIX_SAVED_IDS 86.\" The real group ID and the saved set-group-ID are changed only if the 87.\" effective user ID is that of the super user. 88.\" I.e. 89.\" .Fn setgid 90.\" function is equal to 91.\" .Fn setegid 92.\" function if the effective user ID is not that of the super user. 93.\" End of block 94The 95.Fn setgid 96function is permitted if the specified ID is equal to the real group ID 97.\" Comment out next line for !_POSIX_SAVED_IDS 98.\" or the saved set-group-ID 99.\" Next line is for Appendix B.4.2.2 case. 100or the effective group ID 101of the process, or if the effective user ID is that of the super user. 102.Pp 103The 104.Fn seteuid 105function 106.Pq Fn setegid 107sets the effective user ID (group ID) of the 108current process. 109The effective user ID may be set to the value 110of the real user ID or the saved set-user-ID (see 111.Xr intro 2 112and 113.Xr execve 2 ) ; 114in this way, the effective user ID of a set-user-ID executable 115may be toggled by switching to the real user ID, then re-enabled 116by reverting to the set-user-ID value. 117Similarly, the effective group ID may be set to the value 118of the real group ID or the saved set-group-ID. 119.Sh RETURN VALUES 120.Rv -std 121.Sh ERRORS 122The functions will fail if: 123.Bl -tag -width Er 124.It Bq Er EPERM 125The user is not the super user and the ID 126specified is not the real, effective ID, or saved ID. 127.El 128.Sh SEE ALSO 129.Xr getgid 2 , 130.Xr getuid 2 , 131.Xr issetugid 2 , 132.Xr setregid 2 , 133.Xr setreuid 2 134.Sh STANDARDS 135The 136.Fn setuid 137and 138.Fn setgid 139functions are compliant with the 140.St -p1003.1-90 141specification with 142.Li _POSIX_SAVED_IDS 143.\" Uncomment next line for !_POSIX_SAVED_IDS 144not 145defined with the permitted extensions from Appendix B.4.2.2. 146The 147.Fn seteuid 148and 149.Fn setegid 150functions are extensions based on the 151.Tn POSIX 152concept of 153.Li _POSIX_SAVED_IDS , 154and have been proposed for a future revision of the standard. 155.Sh HISTORY 156A 157.Fn setuid 158and a 159.Fn setgid 160function calls appeared in 161.At v7 . 162