Add shell expansion for output lines

Do shell expansion for output lines (|, @ and ?), so that it is possible to
evaluate arbitrary shell expressions.

Other fixes included:
- Don't assume ksh is in bin.
- Eval commands using the standard shell instead of ksh.
- Make sure we delete temp files; also avoid creating a temp file per line.
- Don't print ? output if return status is 0.
- Fix literal \? match when evaluating lines.

ts

@@ -1,18 +1,14 @@
-#!/bin/ksh
+#!/usr/bin/env ksh
 
 function tsrun
 {
-	typeset err out ret
+	typeset ret
 
-	err=$(mktemp /tmp/XXXXXXXXXX)
+	sh -c "$@" >$out 2>$err
-	out=$(mktemp /tmp/XXXXXXXXXX)
-	trap "rm $err $out" EXIT
-
-	eval "$@" >$out 2>$err
 	ret=$?
 	sed 's/^/| /' $out
 	sed 's/^/@ /' $err
-	print '? '$ret
+	(( ret != 0 )) && print "? $ret"
 }
 
 function tseval
@@ -26,15 +22,37 @@ function tseval
 			print "$ln"
 			tsrun "${ln#$}"
 			;;
-		!(?|@|\|))
+		!(\?|@|\|))
 			print "$ln"
 			;;
 		esac
 	done
 }
 
+function tsexpand
+{
+	typeset ln
+
+	while read ln
+	do
+		case ${ln%% *}
+		in
+			\?|@|\|)
+				eval print \""$ln"\"
+				;;
+			*)
+				print "$ln"
+				;;
+		esac
+	done
+}
+
 (( $# == 0 )) && exit 64
 
+err=$(mktemp /tmp/XXXXXXXXXX)
+out=$(mktemp /tmp/XXXXXXXXXX)
+trap "rm $err $out" HUP INT QUIT TERM
+
 if [[ $1 = -b ]]
 then
 	(( $# == 1 )) && exit 64
@@ -45,8 +63,13 @@ then
 		(rm $fn && tseval >$fn) <$fn
 	done
 else
+	exp=$(mktemp /tmp/XXXXXXXXXX)
+	trap "rm $exp" HUP INT QUIT TERM
 	for fn
 	do
-		tseval <$fn | diff -u $fn -
+		tsexpand <$fn >$exp
+		tseval <$fn | diff -u $exp -
 	done
+	rm $exp
 fi
+rm $err $out