> From: "Todd C. Miller" <[email protected]>
> Date: Sat, 16 Jun 2018 06:37:03 -0600
>
> On Tue, 12 Jun 2018 02:35:57 +0200, Alexander Hall wrote:
>
> > The diff below uses system(3) to call /usr/bin/clear, fiddling with
> > *env() to make sure the current TERM value is propagated. The error
> > handling is deliberately sparse, since I don't know what the reasonable
> > error actions would be.
> >
> > It's quite possible there already exists a better function to call
> > within the ksh code already, but I was unable to figure out which if so.
>
> Using system() within ksh seems wrong. How about this instead?
To e honest, I find the whole idea of invoking an external program to
clear the screen insane.
> Index: bin/ksh/emacs.c
> ===================================================================
> RCS file: /cvs/src/bin/ksh/emacs.c,v
> retrieving revision 1.84
> diff -u -p -u -r1.84 emacs.c
> --- bin/ksh/emacs.c 16 Jan 2018 17:17:18 -0000 1.84
> +++ bin/ksh/emacs.c 16 Jun 2018 12:31:59 -0000
> @@ -146,6 +146,7 @@ static int isu8cont(unsigned char);
> /* proto's for keybindings */
> static int x_abort(int);
> static int x_beg_hist(int);
> +static int x_clear_screen(int);
> static int x_comp_comm(int);
> static int x_comp_file(int);
> static int x_complete(int);
> @@ -202,6 +203,7 @@ static int x_debug_info(int);
> static const struct x_ftab x_ftab[] = {
> { x_abort, "abort", 0 },
> { x_beg_hist, "beginning-of-history", 0 },
> + { x_clear_screen, "clear-screen", 0 },
> { x_comp_comm, "complete-command", 0 },
> { x_comp_file, "complete-file", 0 },
> { x_complete, "complete", 0 },
> @@ -1004,12 +1006,19 @@ x_draw_line(int c)
> {
> x_redraw(-1);
> return KSTD;
> +}
>
> +static int
> +x_clear_screen(int c)
> +{
> + x_redraw(-2);
> + return KSTD;
> }
>
> -/* Redraw (part of) the line. If limit is < 0, the everything is redrawn
> - * on a NEW line, otherwise limit is the screen column up to which needs
> - * redrawing.
> +/* Redraw (part of) the line.
> + * A non-negative limit is the screen column up to which needs
> + * redrawing. A limit of -1 redraws on a new line, while a limit
> + * of -2 (attempts to) clear the screen.
> */
> static void
> x_redraw(int limit)
> @@ -1018,9 +1027,20 @@ x_redraw(int limit)
> char *cp;
>
> x_adj_ok = 0;
> - if (limit == -1)
> + if (limit == -2) {
> + char *term = str_val(global("TERM"));
> + int ret = -1;
> + if (term && *term) {
> + Source *sold = source;
> + ret = command("/usr/bin/clear", 0);
> + source = sold;
> + }
> + if (ret != 0)
> + x_e_putc('\n');
> + }
> + else if (limit == -1)
> x_e_putc('\n');
> - else
> + else if (limit >= 0)
> x_e_putc('\r');
> x_flush();
> if (xbp == xbuf) {
> Index: bin/ksh/ksh.1
> ===================================================================
> RCS file: /cvs/src/bin/ksh/ksh.1,v
> retrieving revision 1.200
> diff -u -p -u -r1.200 ksh.1
> --- bin/ksh/ksh.1 30 May 2018 21:20:52 -0000 1.200
> +++ bin/ksh/ksh.1 16 Jun 2018 12:29:34 -0000
> @@ -4690,6 +4690,10 @@ Moves the cursor to the beginning of the
> Uppercase the first character in the next
> .Ar n
> words, leaving the cursor past the end of the last word.
> +.It clear-screen:
> +Attempts to clears the screen by invoking
> +.Xr clear 1
> +and redraws the prompt and current input line.
> .It comment: ^[#
> If the current line does not begin with a comment character, one is added at
> the beginning of the line and the line is entered (as if return had been
>
>
