uswitch(2)							System Calls Manual							uswitch(2)

NAME

       uswitch - Get or set compatibility environment specific behavior for a calling process through the uswitch value.

SYNOPSIS

       #include <sys/uswitch.h>

       long uswitch(
	       long cmd,
	       long mask );

PARAMETERS

       Specifies the requested actions. The valid cmd values are: Returns the current uswitch value for the calling process.  If mask is non-zero,
       it returns the status of specific uswitch bit-mask(s).  Changes the current uswitch value for the calling process as specified by the  mask
       bit-mask(s).   The  following  bit-masks  are valid when specified with either of the values for the cmd parameter: Specifies System V NULL
       pointer behavior.  Specifies process requests enhanced core file naming.

DESCRIPTION

       The uswitch system call is used to get or change the compatibility environment specific behavior in Tru64 UNIX.	 Any  changes  affect  the
       calling process and its children.

       When  the  USW_NULLP  bit of uswitch is set to 1, the System V method of treating NULL pointers is applied. In this method, references to a
       NULL pointer always returns zero (0).  When this bit-mask is reset to zero (0), subsequent references to a NULL pointer generate a  segmen-
       tation violation signal (SIGSEGV).

       When  the  USW_CORE  bit  of uswitch is set to 1, the process requests enhanced core file naming.  The bit-mask, when set, can be inherited
       when the process forks.	The bit-mask is cleared when an exec system call is executed.  See core(4) for more information about core files.

       Any write(2) references to NULL pointers generate a segmentation violation signal (SIGSEGV) regardless of the uswitch value.

NOTES

       Usage of this system call may make the application non-portable.

RETURN VALUES

       Upon successful completion, either the current or new uswitch value for mask is returned.  Otherwise, a value of -1 is returned	and  errno
       is set to indicate the error.

ERRORS

       If  the	uswitch system call fails, the uswitch value remains unchanged and errno is set to the following: The mask is greater than USW_MAX
       or less than USW_MIN.

EXAMPLES

       The following code sample sets the bit mask for System V NULL pointer behavior:

	      long uswitch_val;

	      ...  uswitch_val = uswitch(USC_GET,0);	      /* Gets current value*/ uswitch(USC_SET, uswitch_val | USW_NULLP); /* Sets USW_NULLP
	      bit */ The following code sample sets the bit mask for enhanced core file names:

	      long uswitch_val;

	      ...   uswitch_val  =  uswitch(USC_GET,0); 	/* Gets current value*/ uswitch(USC_SET, uswitch_val | USW_CORE); /* Sets USW_CORE
	      bit */

																	uswitch(2)