xterm title/screen title+hardstatus

["Glenn F. Maynard" <glennm@mediaone.net>]

I've been trying to solve the problems with getting reliable titles and
hardstatus lines (for screen).

Two major problems: dealing with all input lines, and following processes
around when job switching.

The first is the more difficult one.  I couldn't get tcsh or bash to do
this; zsh has come the closest.  In particular, there're issues with
dealing with commands containing single quotes, double quotes, both nested,
and escaping.  Zsh handles the quoting issue fine (tcsh can't seem to do
it at all; simple things like perl -e 'print "Hello";' become a major
task.)  Dealing with escapes is much more difficult (from preexec):
preexec appears to receive the original, unparsed input command (including
whitespace)--except that escapes are parsed, so a command like
echo "Hello\nThere\n"; contains two real newlines, not the character
sequence "\n".  I don't know if this is intentional: the rest of the
preexec parameters seem completely unparsed (no parameter parsing, no
variable substitution, no whitespace stripping), so my guess is that it
is.  Passing the string through the "escape everything" command is no good,
since it escapes quotes and everything else that hasn't been touched.  My
objective is to display exactly what was typed in the titlebar (parsed
somewhat: the first word, the command, is placed in the title; the remainder,
if anything, is placed in the hardstatus line.)

The second is a bit easier, especially since zsh provides $jobtexts[].  It
needs a bit of help from the shell; it'd be silly to reimplement getjob()
in shell code (since it'd need to be updated if new job codes are introduced.)
I wasn't sure where this should be added, however.  Currently, I've added a
variable expansion parameter: if FOO=%vi, then ${(J)FOO} expands to the job
number.  The patch has at least two problems: first, I couldn't find anything
to pass as a command name to the second argument of getjob(), so any errors
in it come from "foo".  Second, errors are bad in this case: if I run an fg
with bad arguments (fg %12345), getjob() says as much, so two errors are
printed (one from preexec calling getjob, and another from fg.)  I'm not sure
how to fix these, or if there's a better way to do this.

Other problems I've had: Whitespace stripping was rather tricky; I'm sure
there's a better way to do it.  The (z) (split) expansion command has very
strange behavior: it splits on spaces if there's more than one word; if
there's only one word, it splits it into an array of single characters.
Is this intentional or a bug? It's very difficult to use; the hack I used
to get around it should be fairly obvious.

The function currently only works in screen; it doesn't handle the case of
being run under xterm (which uses a different escape and only handles
a single title setting; screen has two, a 20ish-character title and an
arbitrary length hard status line.)  If someone wants to use the script
as is in screen, use 

hardstatus string "%t%?: %h%?"

in .screenrc to display both.

Patch (with above listed flaws); written for 3.1.9-dev-7, applies against CVS:

diff -ur zsh-3.1.9-dev-7/Src/jobs.c zsh-3.1.9.dev7-job/Src/jobs.c
--- zsh-3.1.9-dev-7/Src/jobs.c	Tue Oct 17 08:57:38 2000
+++ zsh-3.1.9.dev7-job/Src/jobs.c	Wed Nov 15 02:07:26 2000
@@ -1089,7 +1089,7 @@
  * to a job number.                                             */
 
 /**/
-static int
+int
 getjob(char *s, char *prog)
 {
     int jobnum, returnval;
diff -ur zsh-3.1.9-dev-7/Src/subst.c zsh-3.1.9.dev7-job/Src/subst.c
--- zsh-3.1.9-dev-7/Src/subst.c	Mon Jun 19 05:14:34 2000
+++ zsh-3.1.9.dev7-job/Src/subst.c	Wed Nov 15 02:54:25 2000
@@ -767,6 +767,7 @@
     char hkeys = 0;
     char hvals = 0;
     int subexp;
+    int joblookup = 0;
 
     *s++ = '\0';
     if (!ialnum(c = *s) && c != '#' && c != Pound && c != '-' &&
@@ -912,6 +913,10 @@
 			goto flagerr;
 		    break;
 
+		case 'J':
+		    joblookup++;
+		    break;
+
 		case 'l':
 		    tt = 1;
 		/* fall through */
@@ -1687,6 +1692,26 @@
 	opts[PROMPTSUBST] = ops;
 	opts[PROMPTBANG] = opb;
 	opts[PROMPTPERCENT] = opp;
+    }
+    if (joblookup) {
+	if (isarr) {
+	    char **ap;
+
+	    if (!copied)
+		aval = arrdup(aval), copied = 1;
+	    ap = aval;
+
+	    for (; *ap; ap++) {
+		int i = getjob(*ap, "foo");
+		*ap = hcalloc(16);
+		sprintf(*ap, "%i", i);
+            }
+	} else {
+	    int i = getjob(val, "foo");
+	    val = hcalloc(16);
+	    sprintf(val, "%i", i);
+	    copied = 1;
+	}
     }
     if (quotemod) {
 	if (--quotetype > 3)

(That allocation could probably be handled better, too, but it wouldn't matter
unless some masochistic person uses a system with 64-bit randomized PIDs.)

Zsh functions:

preexec() {
	local cmd spl pnum lhs rhs
	cmd=$@
	
	while [[ $cmd == *\  ]] do cmd=${cmd% } ; done
	while [[ $cmd == \ * ]] do cmd=${cmd# } ; done
# bug? ${(z)xxx} should split a string into an array of words; but if there
# is only 1 word, we get an array of chars. work around this.

	spl=${(z)cmd}
	if [[ ${#spl} == ${#cmd} ]] then
		# it was split into an array of chars
		lhs=${cmd}
		rhs=
	else
		lhs=${spl[1]}
		shift spl
		rhs=${spl[*]}
	fi

	# strip off any path from lhs
	lhs=${lhs:t}
	# is this a command which restarts an existing job?
	# lhs "fg"
	if [[ $lhs == "fg" ]] then
		pnum=${(J)rhs}
		preexec ${jobtexts[$pnum]}
		return
	fi

	# lhs %*?
	if [[ $lhs == %* ]] then
		pnum=${(J)lhs}
		preexec ${jobtexts[$pnum]}
		return
	fi

	echo -n '\033k'$lhs'\033'\\
	echo -n '\033_'$rhs'\033'\\
}

precmd() {
	echo -n '\033kzsh\033\\\033_'$PWD'\033'\\
}

-- 
Glenn Maynard