issetugid(2)

NAME

     issetugid -  determine  if  current  executable  is  running
     setuid or setgid

SYNOPSIS

     #include <unistd.h>

     int issetugid(void);

DESCRIPTION

     The issetugid() function enables library functions (in  lib-
     termlib,   libc,  or  other  libraries)  to  guarantee  safe
     behavior when  used  in  setuid  or  setgid  programs.  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 specified 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  executable  file
     modes  are  setuid  or setgid, or if the existing process is
     executing the new image with uid != euid  or  gid  !=  egid,
     issetugid() will return 1 in the new process.

RETURN VALUES

     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(). Otherwise it returns 0.

ERRORS

     The issetugid() function is  always  successful.  No  return
     value is reserved to indicate an error.

ATTRIBUTES

     See attributes(5) for descriptions of the  following  attri-
     butes:

     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | Interface Stability         | Evolving                    |
    |_____________________________|_____________________________|
    | MT-Level                    | Async-Signal-Safe           |
    |_____________________________|_____________________________|

SEE ALSO

     exec(2), fork(2), setuid(2), getenv(3C), attributes(5)