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SETUID(2)		    BSD System Calls Manual		     SETUID(2)

NAME
     setuid, seteuid, setgid, setegid — set user and group ID

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <unistd.h>

     int
     setuid(uid_t uid);

     int
     seteuid(uid_t euid);

     int
     setgid(gid_t gid);

     int
     setegid(gid_t egid);

DESCRIPTION
     The setuid() function sets the real and effective user IDs and the saved
     set-user-ID of the current process to the specified value.	 The setuid()
     function is permitted if the specified ID is equal to the real user ID of
     the process, or if the effective user ID is that of the super user.

     The setgid() function sets the real and effective group IDs and the saved
     set-group-ID of the current process to the specified value.  The setgid()
     function is permitted if the specified ID is equal to the real group ID
     of the process, or if the effective user ID is that of the super user.
     Supplementary group IDs remain unchanged.

     The seteuid() function (setegid()) sets the effective user ID (group ID)
     of the current process.  The effective user ID may be set to the value of
     the real user ID or the saved set-user-ID (see intro(2) and execve(2));
     in this way, the effective user ID of a set-user-ID executable may be
     toggled by switching to the real user ID, then re-enabled by reverting to
     the set-user-ID value.  Similarly, the effective group ID may be set to
     the value of the real group ID or the saved set-group-ID.

RETURN VALUES
     Upon success, these functions return 0; otherwise -1 is returned.

     If the user is not the super user, or the uid specified is not the real,
     effective ID, or saved ID, these functions return -1.

SEE ALSO
     getgid(2), getgroups(2), getuid(2)

STANDARDS
     The setuid() and setgid() functions are compliant with the ISO/IEC
     9945-1:1990 (“POSIX.1”) specification with _POSIX_SAVED_IDS not defined.
     We do not implement the _POSIX_SAVED_IDS option as specified in the stan‐
     dard because this would make it impossible for a set-user-ID executable
     owned by a user other than the super-user to permanently revoke its priv‐
     ileges.

     The seteuid() and setegid() functions are compliant with IEEE Std
     1003.1-2001 (“POSIX.1”).

HISTORY
     The setuid() and setgid() functions appeared in Version 2 AT&T UNIX and
     Version 4 AT&T UNIX, respectively.

BSD				 April 3, 2010				   BSD

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