From: "Brian F. Feldman" <green@...>
Date: 2001-09-01T14:05:54+09:00
Subject: [ruby-talk:20655] Re: Changing a program's name at run time via $0...

Sean Chittenden <sean-ruby-talk@chittenden.org> wrote:
> 	Anyone have any ideas how to change a program's name while it's 
> being executed (specifically on FreeBSD)?
> 
> #!/usr/local/bin/ruby -w
> $0 = 'other_name'
> sleep(60)
> 
> 	(quickly dash to another keyboard and type ps (auxwww|-ef))  
> Doesn't seem to work...  <:~( Anyone else have any luck trying this or 
> thoughts on how to get it to work?  -sc

Ruby needs to be updated to use setproctitle(3) on platforms which have it.
E.g. I get:

irb(main):012:0> puts `ps p #{$$}`.split(/\n/)[1]
20276  p5  S+     0:00.98 ruby: irb (ruby)
nil
irb(main):013:0> $0 = "proctitle!"
"proctitle!"
irb(main):014:0> puts `ps p #{$$}`.split(/\n/)[1]
20276  p5  S+     0:01.07 ruby: proctitle! (ruby)
nil

if I apply this change:

--- ruby.c	2001/07/14 15:17:19	1.49
+++ ruby.c	2001/09/01 05:05:28
@@ -885,7 +885,7 @@
     static int len;
 
     if (origargv == 0) rb_raise(rb_eRuntimeError, "$0 not initialized");
-#ifndef __hpux
+#if !defined(__hpux) && !defined(__FreeBSD__) && !defined(__NetBSD__)
     if (len == 0) {
 	s = origargv[0];
 	s += strlen(s);
@@ -900,20 +900,7 @@
     StringValue(val);
     s = RSTRING(val)->ptr;
     i = RSTRING(val)->len;
-#ifndef __hpux
-    if (i < len) {
-	memcpy(origargv[0], s, i);
-	origargv[0][i] = '\0';
-    }
-    else {
-	memcpy(origargv[0], s, i);
-	s = origargv[0]+i;
-	*s++ = '\0';
-	while (++i < len)
-	    *s++ = ' ';
-    }
-    rb_progname = rb_tainted_str_new2(origargv[0]);
-#else
+#ifdef __hpux
     if (i >= PST_CLEN) {
       union pstun j;
       j.pst_command = s;
@@ -928,6 +915,22 @@
       pstat(PSTAT_SETCMD, j, i, 0, 0);
     }
     rb_progname = rb_tainted_str_new(s, i);
+#elif defined(__FreeBSD__) || defined(__NetBSD__)
+    setproctitle("%.*s", i, s);
+    rb_progname = rb_tainted_str_new(s, i);
+#else
+    if (i < len) {
+	memcpy(origargv[0], s, i);
+	origargv[0][i] = '\0';
+    }
+    else {
+	memcpy(origargv[0], s, i);
+	s = origargv[0]+i;
+	*s++ = '\0';
+	while (++i < len)
+	    *s++ = ' ';
+    }
+    rb_progname = rb_tainted_str_new2(origargv[0]);
 #endif
 }
 

-- 
 Brian Fundakowski Feldman           \  FreeBSD: The Power to Serve!  /
 green@FreeBSD.org                    `------------------------------'