ISSETUGID(2) BSD System Calls Manual ISSETUGID(2)
issetugid -- is current executable running setuid or setgid
The issetugid() function returns 1 if the process was made setuid or set-
gid as the result of the last or other previous execve() system calls.
Otherwise it returns 0.
This system call exists so that library routines (inside libtermlib,
libc, or other libraries) can guarantee safe behavior when used inside
setuid or setgid programs. Some library routines may be passed insuffi-
cient information and hence not know whether the current program was
started setuid or setgid because higher level calling code may have made
changes to the uid, euid, gid, or egid. Hence these low-level library
routines are unable to determine if they are being run with elevated or
In particular, it is wise to use this call to determine if a pathname
returned from a getenv() call may safely be used to open() the specified
file. Quite often this is not wise because the status of the effective
uid is not known.
The issetugid() system call's result is unaffected by calls to setuid(),
setgid(), or other such calls. In case of a fork(), the child process
inherits the same status.
The status of issetugid() is only affected by execve(). If a child
process executes a new executable file, a new issetugid status will be
determined. This status is based on the existing process's uid, euid,
gid, and egid permissions and on the modes of the executable file. If
the new executable file modes are setuid or setgid, or if the existing
process is executing the new image with uid != euid or gid != egid, the
new process will be considered issetugid.
The issetugid() function is always successful, and no return value is
reserved to indicate an error.
execve(2), setegid(2), seteuid(2), setgid(2), setuid(2), getenv(3)
The issetugid() function call first appeared in OpenBSD 2.0.
BSD March 28, 2017 BSD