add $plan9 variable

man/man7/plumb.7

diff --git a/man/man7/plumb.7 b/man/man7/plumb.7
index a3c10e1..82c771b 100644
--- a/man/man7/plumb.7
+++ b/man/man7/plumb.7
@@ -337,6 +337,11 @@
 The contents of the
 .B wdir
 field of the message.
+.TP
+.B $plan9
+The root directory of the Plan 9 tree
+(see
+.IR get9root (3)).
 .RE
 .SH EXAMPLE
 The following is a modest, representative file of plumbing rules.

plumb/basic

diff --git a/plumb/basic b/plumb/basic
index 464b954..4edd432 100644
--- a/plumb/basic
+++ b/plumb/basic
@@ -58,7 +58,7 @@
 data matches '([a-zA-Z¡-￿0-9_\-./]+)\.(jpe?g|JPE?G|gif|GIF|tiff?|TIFF?|ppm|bit|png|PNG)'
 arg isfile	$0
 plumb to image
-plumb start qiv -t $file
+plumb start page $file
 
 # postscript/pdf/dvi go to page but not over the a plumb port
 # the port is here for reference but is unused
@@ -67,8 +67,7 @@
 data matches '([a-zA-Z¡-￿0-9_\-./]+)\.(ps|PS|eps|EPS|pdf|PDF|dvi|DVI)'
 arg isfile	$0
 plumb to postscript
-plumb start psv $file
-# plumb start page -w $file
+plumb start page $file
 
 # open office - s[xt][cdigmw], doc, xls, ppt
 data matches '[a-zA-Z¡-￿0-9_\-./]+'
@@ -104,10 +103,10 @@
 plumb to edit
 plumb client $editor
 
-# .h files are looked up in /usr/local/plan9/include and passed to edit
+# .h files are looked up in $plan9/include and passed to edit
 type is text
 data matches '([a-zA-Z¡-￿0-9]+\.h)('$addr')?'
-arg isfile	/usr/local/plan9/include/$1
+arg isfile	$plan9/include/$1
 data set	$file
 attr add	addr=$3
 plumb to edit
@@ -138,9 +137,9 @@
 dst is image
 arg isfile $data
 plumb to image
-plumb start qiv -t $data
+plumb start page $data
 
 # start rule for postscript without known suffixes
 dst is postscript
 arg isfile $data
-plumb start gv $data
+plumb start page $data

src/cmd/plumb/rules.c

diff --git a/src/cmd/plumb/rules.c b/src/cmd/plumb/rules.c
index ab27787..be67532 100644
--- a/src/cmd/plumb/rules.c
+++ b/src/cmd/plumb/rules.c
@@ -531,6 +531,11 @@
 	Ruleset *rs;
 	Rule *r;
 	int eof, inrule, i, ncmd;
+	char *plan9root;
+
+	plan9root = get9root();
+	if(plan9root)
+		setvariable("plan9", 5, plan9root, plan9root);
 
    Again:
 	eof = 0;