bsd man page for setreuid

SETREUID(2)							System Calls Manual						       SETREUID(2)

NAME
       setreuid - set real and effective user ID's

SYNOPSIS
       setreuid(ruid, euid)
       int ruid, euid;

DESCRIPTION
       The  real  and  effective  user	ID's of the current process are set according to the arguments.  If ruid or euid is -1, the current uid is
       filled in by the system.  Unprivileged users may change the real user ID to the effective user ID and vice-versa; only the  super-user  may
       make other changes.

RETURN VALUE
       Upon successful completion, a value of 0 is returned.  Otherwise, a value of -1 is returned and errno is set to indicate the error.

ERRORS
       [EPERM]	      The  current  process  is  not the super-user and a change other than changing the effective user-id to the real user-id was
		      specified.

SEE ALSO
       getuid(2), setregid(2), setuid(3)

4th Berkeley Distribution					    May 9, 1985 						       SETREUID(2)