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VT100/UNIX                          Aegis                           VT100/UNIX



NAME
     vt100/unix - Using the vt100 emulator with a Remote UNIX System Running
     'termcap'

DESCRIPTION
     The following are some tips for using the vt100 emulator when the remote
     host is a UNIX system that has the termcap facility.

     Most users set the term and termcap environment variables by running the
     BSD 'tset' program (/bsd4.3/usr/ucb/tset) in their .login or .profile
     startup files.  When logging in to UNIX system through the vt100
     emulator, you should specify that your terminal is a vt132, which is a
     vt100 with insert/delete character and insert/delete lines capabilities.
     The only difference is that a real vt132 is always 24 lines by 80
     columns, and the emulator will use as many lines and columns as will fit
     in the DM window.  However, you can automatically modify your termcap
     variable at login time so that the li and co capabilities reflect the
     actual size of the emulator screen.  To do so, place the following two
     lines,  or something similar, in your .login file (this would need to be
     changed slightly for use in a .profile file):


           tset -Q -I -s vt132 >tset1.$$; setsize <tset1.$$ >tset.$$
           source tset.$$; stty nl0; rm tset.$$ tset1.$$


     where setsize is the following c-shell script:


           #!/bin/csh
           set size=`sz`
           set lines=$size[1]
           set columns=$size[2]
           sed -e "s/li#[0-9]*:/li#${lines}:/" -e "s/co#[0-9]*:/co#${columns}:/"


     and sz is a C program, shown below:


       #include <stdio.h>
       #include <sgtty.h>
       #include <sys/file.h>

       main()
       {
           FILE *fp;
           int fd, lines, columns;
           struct sgttyb otty, ntty;

           if ((fd = open("/dev/tty",O_RDWR,777)) < 0)
                   perror("open"), exit(1);
           if ((fp = fdopen(fd, "r")) == NULL)
                   perror("fdopen"), exit(2);
           if (gtty(fd, &otty) < 0)
                   perror("gtty"), exit(3);
           ntty = otty;
           ntty.sg_flags = (ntty.sg_flags & ~ECHO) | RAW;
           stty(fd, &ntty);
           write(fd, "\033[50n", 5);
           fscanf(fp, "\033[%d;%dS", &lines, &columns);
           stty(fd, &otty);
           printf("%d %d\n", lines, columns);
           close(fd);
       }


     This program sends ESC[50n to the emulator.  This is a non-standard
     escape sequence,  in response to which the emulator sends back the
     current screen size, in the form ESC[nn;mmS, where nn is the number of
     lines, and mm is the number of columns.

     Note:
          In order for programs such as 'vi' to work properly in windows
          larger than 24 lines, there is one change you must make to the
          termcap entry for   vt100.  The sf (scroll forward) capability is
          given as sf=30\E7\E[24H\ED\E8.  This works by saving the cursor (ESC
          7), moving to the bottom line (ESC[24H, which moves the cursor to
          the 24th line), doing an index operation (ESC D), and restoring the
          cursor (ESC 8).  The problem, of course, is that line 24 may not be
          the bottom line.  This can be fixed by changing the 24 to some very
          large number, say 200, since trying to move the cursor outside the
          bounds of the screen always causes it to be placed at the edge of
          the screen.  Thus this change is safe to make, even when a real
          vt100 terminal is being used.