clear for vax/vms

[Col. G. L. Sicherman]

This program clears the screen under VAX/VMS.  I haven't figured out
how to suppress the error message that says there are no error messages.
-----
/*
 *      clear the screen.  (why is there no command for this?)
 *      Col. Sicherman.  10 Jun 1985.
 */
#define BUFLEN  18
#define SMG$K_ERASE_WHOLE_DISPLAY       474
#include <descrip.h>
#include <dvidef.h>
#include <iodef.h>
#include <stdio.h>
char *outname = "sys$output";
struct dsc$descriptor_s stringp;
main()
{
        short int chan;
        long int s, termtype, event, retlen, termtable, x, y;
        char databuf[BUFLEN];
        stringp.dsc$b_dtype = 1;
        stringp.dsc$b_class = DSC$K_DTYPE_T;
        stringp.dsc$a_pointer = outname;
        stringp.dsc$w_length = strlen(outname);
        s = sys$assign(&stringp, &chan, 0,0);
        if (!(1&s)) {
                fprintf(stderr,
                "CLEAR: ERROR %ld IN ASSIGNING SYS$OUTPUT\n",s);
                exit(1);
        }
        x = DVI$_DEVTYPE;
        s = lib$getdvi(&x, &chan, 0, &termtype);
        if (!(1&s)) {
                fprintf(stderr,"CLEAR: CANNOT GET DEVICE TYPE\n");
                exit(1);
        }
        s=smg$init_term_table_by_type(&termtype, &termtable);
        if (!(1&s)) {
                fprintf(stderr,"CLEAR: UNKNOWN TERM TYPE\n");
                exit(1);
        }
        x = SMG$K_ERASE_WHOLE_DISPLAY;
        y = BUFLEN;
        s = smg$get_term_data(&termtable, &x, &y, &retlen, databuf, 0);
        if (!(1&s)) {
                fprintf(stderr,"CLEAR: CANNOT GET CLEAR SEQUENCE\n");
                exit(1);
        }
        if (!retlen) {
                fprintf(stderr,"CLEAR: NO CLEAR SEQUENCE\n");
                exit(1);
        }
        s = LIB$GET_EF(&event);
        if (!(1&s)) {
                fprintf(stderr,"CLEAR: CANNOT GET EVENT FLAG\n");
                exit(1);
        }
        s = SYS$QIOW(event,chan,
        IO$_WRITEVBLK,0,0,0,databuf,retlen,0,0,0,0);
        if (!(1&s)) {
                fprintf(stderr, "CLEAR: ERROR %ld IN WRITING\n",s);
                exit(1);
        }
        s = LIB$FREE_EF(&event);
        if (!(1&s)) {
                fprintf(stderr,"CLEAR: CANNOT FREE EVENT FLAG\n");
                exit(1);
        }
        exit(0);
}
-- 
Col. G. L. Sicherman
...{rocksvax|decvax}!sunybcs!colonel