osf1 man page for setgid

setgid(2)							System Calls Manual							 setgid(2)

NAME
       setgid - Sets the group ID

SYNOPSIS
       #include <unistd.h>

       int setgid (
	       gid_t group_id );

       Application  developers	may  want  to  specify an #include statement for <sys/types.h> before the one for <unistd.h> if programs are being
       developed for multiple platforms. The additional #include statement is not required on Tru64 UNIX systems or by ISO  or	X/Open	standards,
       but may be required on other vendors' systems that conform to these standards.

STANDARDS
       Interfaces documented on this reference page conform to industry standards as follows:

       setgid():  POSIX.1, XPG4, XPG4-UNIX

       Refer to the standards(5) reference page for more information about industry standards and associated tags.

PARAMETERS
       Specifies the new group ID.

DESCRIPTION
       The setgid() function sets the real group ID, effective group ID, and the saved set group ID to the value specified by the group_id parame-
       ter.

       If the process does not have superuser privilege, but the group_id parameter is equal to the real group ID or the saved set group  ID,  the
       setgid() function sets the effective group ID to group_id.  The real group ID and saved set group ID remain unchanged.

       Any supplementary group IDs of the calling process remain unchanged.

RETURN VALUES
       Upon  successful  completion,  the  setgid()  function returns 0 (zero).  Otherwise, the function returns -1 and sets errno to indicate the
       error.

ERRORS
       The setgid() function sets errno to the specified values for the following conditions: The value of the group_id parameter is invalid.  The
       process does not have superuser privilege and the group_id parameter does not match the real group ID or the saved set group ID.

RELATED INFORMATION
       Functions: exec(2), getgid(2), setuid(2)

       Standards: standards(5) delim off

																	 setgid(2)