[9fans] 9vx patch to read environment var PLAN9

[EBo]

The following is a little patch to 9vx which uses getenv to read the
environmental variable PLAN9 to set "plan 9 root" on startup if it has not
been overloaded on the command line or in the CWD.  I would enjoy any feedback.

Best regards,

  EBo --

=====================================================================

diff -r 8184025094f4 src/9vx/main.c                
--- a/src/9vx/main.c    Mon Oct 05 02:53:41 2009 -0400
+++ b/src/9vx/main.c    Sun Apr 11 11:59:03 2010 -0500
@@ -10,6 +10,8 @@

 #include       "u.h"
 #include       "libvx32/vx32.h"
+#include       <stdlib.h>
+#include       <string.h>
 #include       <sys/mman.h>
 #include       <signal.h>
 #include       <pwd.h>
@@ -224,12 +226,13 @@
 findroot(void)
 {
        static char cwd[1024];
+       static char plan9[1024];
        int i;
        char buf[1024];
        char *dir[] = {
                cwd,
-               "/Users/rsc/9vx",
-               "/home/rsc/plan9/4e"
+               plan9,
+               "/usr/local/plan9"
        };

        if(getcwd(cwd, sizeof cwd) == nil){
@@ -237,6 +240,9 @@
                panic("getcwd: %r");
        }

+       if(getenv("PLAN9") != nil)
+               strncpy(plan9, getenv("PLAN9"), sizeof plan9);
+
        for(i=0; i<nelem(dir); i++){
                snprint(buf, sizeof buf, "%s/386/bin/rc", dir[i]);
                if(access(buf, 0) >= 0)