Infrastructure and commands to manage the environment for processes started

within tmux.

There is a global environment, copied from the external environment when the
server is started and each sesssion has an (initially empty) session
environment which overrides it.

New commands set-environment and show-environment manipulate or display the
environments.

A new session option, update-environment, is a space-separated list of
variables which are updated from the external environment into the session
environment every time a new session is created - the default is DISPLAY.

environ.c

@@ -0,0 +1,147 @@
+/* $OpenBSD$ */
+
+/*
+ * 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.
+ */
+
+#include <sys/types.h>
+
+#include <stdlib.h>
+#include <string.h>
+
+#include "tmux.h"
+
+/*
+ * Environment - manipulate a set of environment variables.
+ */
+
+RB_GENERATE(environ, environ_entry, entry, environ_cmp);
+
+void	environ_set1(struct environ *, char *, char *);
+
+int
+environ_cmp(struct environ_entry *envent1, struct environ_entry *envent2)
+{
+	return (strcmp(envent1->name, envent2->name));
+}
+
+void
+environ_init(struct environ *env)
+{
+	RB_INIT(env);
+}
+
+void
+environ_free(struct environ *env)
+{
+	struct environ_entry	*envent;
+
+	while (!RB_EMPTY(env)) {
+		envent = RB_ROOT(env);
+		RB_REMOVE(environ, env, envent);
+		xfree(envent->name);
+		if (envent->value != NULL)
+			xfree(envent->value);
+		xfree(envent);
+	}
+}
+
+void
+environ_copy(struct environ *srcenv, struct environ *dstenv)
+{
+	struct environ_entry	*envent;
+
+	RB_FOREACH(envent, environ, srcenv)
+		environ_set(dstenv, envent->name, envent->value);
+}
+
+struct environ_entry *
+environ_find(struct environ *env, const char *name)
+{
+	struct environ_entry	envent;
+
+	envent.name = (char *) name;
+	return (RB_FIND(environ, env, &envent));
+}
+
+void
+environ_set(struct environ *env, const char *name, const char *value)
+{
+	struct environ_entry	*envent;
+
+	if ((envent = environ_find(env, name)) != NULL) {
+		if (envent->value != NULL)
+			xfree(envent->value);
+		if (value != NULL)
+			envent->value = xstrdup(value);
+		else
+			envent->value = NULL;
+	} else {
+		envent = xmalloc(sizeof *envent);
+		envent->name = xstrdup(name);
+		if (value != NULL)
+			envent->value = xstrdup(value);
+		else
+			envent->value = NULL;
+		RB_INSERT(environ, env, envent);
+	}
+}
+
+void
+environ_put(struct environ *env, const char *var)
+{
+	char		*name, *value;
+
+	value = strchr(var, '=');
+	if (value == NULL)
+		return;
+	value++;
+
+	name = xstrdup(var);
+	name[strcspn(name, "=")] = '\0';
+
+	environ_set(env, name, value);
+	xfree(name);
+}
+
+void
+environ_unset(struct environ *env, const char *name)
+{
+	struct environ_entry	*envent;
+
+	if ((envent = environ_find(env, name)) == NULL)
+		return;
+	RB_REMOVE(environ, env, envent);
+	xfree(envent->name);
+	if (envent->value != NULL)
+		xfree(envent->value);
+	xfree(envent);
+}
+
+void
+environ_update(const char *vars, struct environ *srcenv, struct environ *dstenv)
+{
+	struct environ_entry	*envent;
+	char			*var, *next;
+
+	vars = next = xstrdup(vars);
+	while ((var = strsep(&next, " ")) != NULL) {
+		if ((envent = environ_find(srcenv, var)) == NULL)
+			environ_set(dstenv, var, NULL);
+		else
+			environ_set(dstenv, envent->name, envent->value);
+	}
+	xfree(vars);
+}