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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
  cmd Specifies the requested actions. The valid cmd values are:

      USC_GET
	  Returns the current uswitch value for the calling process.  If mask
	  is non-zero, it returns the status of specific uswitch bit-mask(s).

      USC_SET
	  Changes the current uswitch value for the calling process as
	  specified by the mask bit-mask(s).

  mask
      The following bit-masks are valid when specified with either of the
      values for the cmd parameter:

      USW_NULLP
	  Specifies System V NULL pointer behavior.

      USW_CORE
	  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 segmentation 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:

  [EINVAL]
      The mask is greater than USW_MAX or less than USW_MIN.

EXAMPLES
   1.  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 */

   2.  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 */

Index for Section 2

Alphabetical listing for U

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