Try to change the window title to match the command running it in. This is done

by reading argv[0] from the process group leader of the group that owns the tty
(tcgetpgrp()). This can't be done portably so some OS-dependent code is
introduced (ugh); OpenBSD, FreeBSD and Linux are supported at the moment.

A new window flag, automatic-rename, is available: if this is set to off, the
window name is not changed. Specifying a name with the new-window, new-session
or rename-window commands will automatically set this flag to off for the
window in question. To disable it entirely set the option to off globally (setw
-g automatic-rename off).

osdep-freebsd.c

@@ -0,0 +1,64 @@
+/* $Id: osdep-freebsd.c,v 1.1 2009-01-20 19:35:03 nicm Exp $ */
+
+/*
+ * Copyright (c) 2009 Nicholas Marriott <nicm@users.sourceforge.net>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER
+ * IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
+ * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#ifdef __FreeBSD__
+
+#include <sys/param.h>
+#include <sys/sysctl.h>
+
+#include <err.h>
+#include <errno.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+char	*get_argv0(pid_t);
+
+char *
+get_argv0(pid_t pgrp)
+{
+	int	mib[4] = { CTL_KERN, KERN_PROC, KERN_PROC_ARGS, 0 };
+        size_t	size;
+	char   *args, *args2, *procname;
+
+	procname = NULL;
+
+	mib[3] = pgrp;
+
+	args = NULL;
+	size = 128;
+	while (size < SIZE_MAX / 2) {
+		size *= 2;
+		if ((args2 = realloc(args, 2 * size)) == NULL)
+			break;
+		args = args2;
+		if (sysctl(mib, 4, args, &size, NULL, 0) == -1) {
+			if (errno == ENOMEM)
+				continue;
+			break;
+		}
+		procname = strdup(args);
+		break;
+	}
+	free(args);
+
+	return (procname);
+}
+
+#endif