osx man page for issetugid

ISSETUGID(2)						      BSD System Calls Manual						      ISSETUGID(2)

NAME
     issetugid -- is current process tainted by uid or gid changes

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <unistd.h>

     int
     issetugid(void);

DESCRIPTION
     The issetugid() system call returns 1 if the process environment or memory address space is considered ``tainted'', and returns 0 otherwise.

     A process is tainted if it was created as a result of an execve(2) system call which had either of the setuid or setgid bits set (and extra
     privileges were given as a result) or if it has changed any of its real, effective or saved user or group ID's since it began execution.

     This system call exists so that library routines (eg: libc, libtermcap) can reliably determine if it is safe to use information that was
     obtained from the user, in particular the results from getenv(3) should be viewed with suspicion if it is used to control operation.

     A ``tainted'' status is inherited by child processes as a result of the fork(2) system call (or other library code that calls fork, such as
     popen(3)).

     It is assumed that a program that clears all privileges as it prepares to execute another will also reset the environment, hence the
     ``tainted'' status will not be passed on.	This is important for programs such as su(1) which begin setuid but need to be able to create an
     untainted process.

ERRORS
     The issetugid() system call is always successful, and no return value is reserved to indicate an error.

SEE ALSO
     execve(2), fork(2), setegid(2), seteuid(2), setgid(2), setregid(2), setreuid(2), setuid(2)

HISTORY
     The issetugid() system call first appeared in OpenBSD 2.0 and was also implemented in FreeBSD 3.0.

BSD
								  August 25, 1996							       BSD