issetugid(2) System Calls issetugid(2)
issetugid - determine if current executable is running setuid or setgid
The issetugid() function enables library functions (in libtermlib,
libc, or other libraries) to guarantee safe behavior when used in
setuid or setgid programs or programs that run with more privileges
after a succesful exec(2). Some library functions might be passed
insufficient information and not know whether the current program was
started setuid or setgid because a higher level calling code might have
made changes to the uid, euid, gid, or egid. These low-level library
functions are therefore unable to determine if they are being run with
elevated or normal privileges.
The issetugid() function should be used to determine if a path name
returned from a getenv(3C) call can be used safely to open the speci-
fied file. It is often not safe to open such a file because the status
of the effective uid is not known.
The result of a call to issetugid() is unaffected by calls to setuid(),
setgid(), or other such calls. In case of a call to fork(2), the child
process inherits the same status.
The status of issetugid() is affected only by execve() (see exec(2)).
If a child process executes a new executable file, a new issetugid()
status will be based on the existing process's uid, euid, gid, and egid
permissions and on the modes of the executable file. If the new exe-
cutable file modes are setuid or setgid, or if the existing process is
executing the new image with uid != euid or gid != egid, or if the per-
mitted set before the call to the exec function is not a superset of
the inheritable set at that time, issetugid() returns 1 in the new
The issetugid() function returns 1 if the process was made setuid or
setgid as the result of the last or a previous call to execve(). Other-
wise it returns 0.
The issetugid() function is always successful. No return value is
reserved to indicate an error.
See attributes(5) for descriptions of the following attributes:
tab() allbox; cw(2.750000i)| cw(2.750000i) lw(2.750000i)|
lw(2.750000i). ATTRIBUTE TYPEATTRIBUTE VALUE Interface StabilityEvolv-
exec(2), fork(2), setuid(2), getenv(3C), attributes(5), privileges(5)
SunOS 5.10 19 Feb 2003 issetugid(2)