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.

Makefile

@@ -25,8 +25,9 @@ SRCS=	attributes.c buffer-poll.c buffer.c cfg.c client-fn.c \
 	cmd-split-window.c cmd-start-server.c cmd-string.c cmd-if-shell.c \
 	cmd-suspend-client.c cmd-swap-pane.c cmd-swap-window.c \
 	cmd-switch-client.c cmd-unbind-key.c cmd-unlink-window.c \
+	cmd-set-environment.c cmd-show-environment.c \
 	cmd-up-pane.c cmd-display-message.c cmd.c \
-	colour.c grid-view.c grid.c input-keys.c \
+	colour.c environ.c grid-view.c grid.c input-keys.c \
 	input.c key-bindings.c key-string.c layout-set.c layout.c log.c \
 	mode-key.c names.c options-cmd.c options.c paste.c procname.c \
 	resize.c screen-redraw.c screen-write.c screen.c server-fn.c \

client.c

@@ -33,6 +33,7 @@
 
 #include "tmux.h"
 
+void	client_send_environ(struct client_ctx *);
 void	client_handle_winch(struct client_ctx *);
 
 int
@@ -95,6 +96,8 @@ server_started:
 	cctx->srv_in = buffer_create(BUFSIZ);
 	cctx->srv_out = buffer_create(BUFSIZ);
 
+	if (cmdflags & CMD_SENDENVIRON)
+		client_send_environ(cctx);
 	if (isatty(STDIN_FILENO)) {
 		if (ioctl(STDIN_FILENO, TIOCGWINSZ, &ws) == -1)
 			fatal("ioctl(TIOCGWINSZ)");
@@ -133,6 +136,19 @@ not_found:
 	return (1);
 }
 
+void
+client_send_environ(struct client_ctx *cctx)
+{
+	char		      **var;
+	struct msg_environ_data	data;
+
+ 	for (var = environ; *var != NULL; var++) {
+		if (strlcpy(data.var, *var, sizeof data.var) >= sizeof data.var)
+			continue;
+		client_write_server(cctx, MSG_ENVIRON, &data, sizeof data);
+	}
+}
+
 int
 client_main(struct client_ctx *cctx)
 {
@@ -242,8 +258,8 @@ client_msg_dispatch(struct client_ctx *cctx)
 			if (hdr.size != sizeof printdata)
 				fatalx("bad MSG_PRINT size");
 			buffer_read(cctx->srv_in, &printdata, sizeof printdata);
-			printdata.msg[(sizeof printdata.msg) - 1] = '\0';
 
+			printdata.msg[(sizeof printdata.msg) - 1] = '\0';
 			cctx->errstr = xstrdup(printdata.msg);
 			return (-1);
 		case MSG_EXIT:

cmd-attach-session.c

@@ -29,7 +29,7 @@ int	cmd_attach_session_exec(struct cmd *, struct cmd_ctx *);
 const struct cmd_entry cmd_attach_session_entry = {
 	"attach-session", "attach",
 	"[-d] " CMD_TARGET_SESSION_USAGE,
-       	CMD_CANTNEST|CMD_STARTSERVER, CMD_CHFLAG('d'),
+       	CMD_CANTNEST|CMD_STARTSERVER|CMD_SENDENVIRON, CMD_CHFLAG('d'),
 	cmd_target_init,
 	cmd_target_parse,
 	cmd_attach_session_exec,
@@ -43,6 +43,7 @@ cmd_attach_session_exec(struct cmd *self, struct cmd_ctx *ctx)
 	struct cmd_target_data	*data = self->data;
 	struct session		*s;
 	struct client		*c;
+	const char		*update;
 	char			*overrides, *cause;
 	u_int			 i;
 
@@ -93,6 +94,10 @@ cmd_attach_session_exec(struct cmd *self, struct cmd_ctx *ctx)
 
 		ctx->cmdclient->session = s;
 		server_write_client(ctx->cmdclient, MSG_READY, NULL, 0);
+
+		update = options_get_string(&s->options, "update-environment");
+		environ_update(update, &ctx->cmdclient->environ, &s->environ);
+
 		server_redraw_client(ctx->cmdclient);
 	}
 	recalculate_sizes();

cmd-new-session.c

@@ -40,7 +40,7 @@ struct cmd_new_session_data {
 const struct cmd_entry cmd_new_session_entry = {
 	"new-session", "new",
 	"[-d] [-n window-name] [-s session-name] [command]",
-	CMD_STARTSERVER|CMD_CANTNEST, 0,
+	CMD_STARTSERVER|CMD_CANTNEST|CMD_SENDENVIRON, 0,
 	cmd_new_session_init,
 	cmd_new_session_parse,
 	cmd_new_session_exec,
@@ -108,6 +108,8 @@ cmd_new_session_exec(struct cmd *self, struct cmd_ctx *ctx)
 {
 	struct cmd_new_session_data	*data = self->data;
 	struct session			*s;
+	struct environ			 env;
+	const char			*update;
 	char				*overrides, *cmd, *cwd, *cause;
 	int				 detached;
 	u_int				 sx, sy;
@@ -184,13 +186,20 @@ cmd_new_session_exec(struct cmd *self, struct cmd_ctx *ctx)
 	else
 		cmd = options_get_string(&global_s_options, "default-command");
 
+	/* Construct the environment. */
+	environ_init(&env);
+	update = options_get_string(&global_s_options, "update-environment");
+	if (ctx->cmdclient != NULL)
+		environ_update(update, &ctx->cmdclient->environ, &env);
+
 	/* Create the new session. */
-	s = session_create(data->newname, cmd, cwd, sx, sy, &cause);
+	s = session_create(data->newname, cmd, cwd, &env, sx, sy, &cause);
 	if (s == NULL) {
 		ctx->error(ctx, "create session failed: %s", cause);
 		xfree(cause);
 		return (-1);
 	}
+	environ_free(&env);
 
 	if (data->winname != NULL) {
 		xfree(s->curw->window->name);

cmd-respawn-window.c

@@ -47,7 +47,7 @@ cmd_respawn_window_exec(struct cmd *self, struct cmd_ctx *ctx)
 	struct window		*w;
 	struct window_pane	*wp;
 	struct session		*s;
-	const char	       **env;
+	struct environ		 env;
 	char		 	*cause;
 
 	if ((wl = cmd_find_window(ctx, data->target, &s)) == NULL)
@@ -64,7 +64,10 @@ cmd_respawn_window_exec(struct cmd *self, struct cmd_ctx *ctx)
 		}
 	}
 
-	env = server_fill_environ(s);
+	environ_init(&env);
+	environ_copy(&global_environ, &env);
+	environ_copy(&s->environ, &env);
+	server_fill_environ(s, &env);
 
 	wp = TAILQ_FIRST(&w->panes);
 	TAILQ_REMOVE(&w->panes, wp, entry);
@@ -72,9 +75,10 @@ cmd_respawn_window_exec(struct cmd *self, struct cmd_ctx *ctx)
  	window_destroy_panes(w);
 	TAILQ_INSERT_HEAD(&w->panes, wp, entry);
 	window_pane_resize(wp, w->sx, w->sy);
-	if (window_pane_spawn(wp, data->arg, NULL, env, &cause) != 0) {
+	if (window_pane_spawn(wp, data->arg, NULL, &env, &cause) != 0) {
 		ctx->error(ctx, "respawn window failed: %s", cause);
 		xfree(cause);
+		environ_free(&env);
 		return (-1);
 	}
 	layout_init(w);
@@ -84,5 +88,6 @@ cmd_respawn_window_exec(struct cmd *self, struct cmd_ctx *ctx)
 	recalculate_sizes();
 	server_redraw_window(w);
 
+	environ_free(&env);
 	return (0);
 }

cmd-set-environment.c

@@ -0,0 +1,88 @@
+/* $OpenBSD$ */
+
+/*
+ * 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"
+
+/*
+ * Set an environment variable.
+ */
+
+int	cmd_set_environment_exec(struct cmd *, struct cmd_ctx *);
+
+const struct cmd_entry cmd_set_environment_entry = {
+	"set-environment", "setenv",
+	"[-gru] " CMD_OPTION_SESSION_USAGE,
+	0, CMD_CHFLAG('g')|CMD_CHFLAG('r')|CMD_CHFLAG('u'),
+	NULL,
+	cmd_option_parse,
+	cmd_set_environment_exec,
+	cmd_option_free,
+	cmd_option_print
+};
+
+int
+cmd_set_environment_exec(struct cmd *self, struct cmd_ctx *ctx)
+{
+	struct cmd_option_data	*data = self->data;
+	struct session		*s;
+	struct environ		*env;
+
+	if (*data->option == '\0') {
+		ctx->error(ctx, "empty variable name");
+		return (-1);
+	}
+	if (strchr(data->option, '=') != NULL) {
+		ctx->error(ctx, "variable name contains =");
+		return (-1);
+	}
+
+	if (data->chflags & CMD_CHFLAG('g'))
+		env = &global_environ;
+	else {
+		if ((s = cmd_find_session(ctx, data->target)) == NULL)
+			return (-1);
+		env = &s->environ;
+	}
+
+	if (data->chflags & CMD_CHFLAG('u')) {
+		if (data->value != NULL) {
+			ctx->error(ctx, "can't specify a value with -u");
+			return (-1);
+		}
+		environ_unset(env, data->option);
+	} else if (data->chflags & CMD_CHFLAG('r')) {
+		if (data->value != NULL) {
+			ctx->error(ctx, "can't specify a value with -r");
+			return (-1);
+		}
+		environ_set(env, data->option, NULL);
+	} else {
+		if (data->value == NULL) {
+			ctx->error(ctx, "no value specified");
+			return (-1);
+		}
+		environ_set(env, data->option, data->value);
+	}
+
+	return (0);
+}

cmd-set-option.c

@@ -85,6 +85,7 @@ const struct set_option_entry set_option_table[] = {
 	{ "status-right-length", SET_OPTION_NUMBER, 0, SHRT_MAX, NULL },
 	{ "status-utf8", SET_OPTION_FLAG, 0, 0, NULL },	
 	{ "terminal-overrides", SET_OPTION_STRING, 0, 0, NULL },
+	{ "update-environment", SET_OPTION_STRING, 0, 0, NULL },
 	{ "visual-activity", SET_OPTION_FLAG, 0, 0, NULL },
 	{ "visual-bell", SET_OPTION_FLAG, 0, 0, NULL },	
 	{ "visual-content", SET_OPTION_FLAG, 0, 0, NULL },

cmd-show-environment.c

@@ -0,0 +1,67 @@
+/* $OpenBSD$ */
+
+/*
+ * 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"
+
+/*
+ * Show environment.
+ */
+
+int	cmd_show_environment_exec(struct cmd *, struct cmd_ctx *);
+
+const struct cmd_entry cmd_show_environment_entry = {
+	"show-environment", "showenv",
+	"[-g] " CMD_TARGET_SESSION_USAGE,
+	0, CMD_CHFLAG('g'),
+	cmd_target_init,
+	cmd_target_parse,
+	cmd_show_environment_exec,
+	cmd_target_free,
+	cmd_target_print
+};
+
+int
+cmd_show_environment_exec(struct cmd *self, struct cmd_ctx *ctx)
+{
+	struct cmd_target_data		*data = self->data;
+	struct session			*s;
+	struct environ			*env;
+	struct environ_entry		*envent;
+
+	if (data->chflags & CMD_CHFLAG('g'))
+		env = &global_environ;
+	else {
+		if ((s = cmd_find_session(ctx, data->target)) == NULL)
+			return (-1);
+		env = &s->environ;
+	}
+
+	RB_FOREACH(envent, environ, env) {
+		if (envent->value != NULL)
+			ctx->print(ctx, "%s=%s", envent->name, envent->value);
+		else
+			ctx->print(ctx, "-%s", envent->name);
+	}
+
+	return (0);
+}

cmd-split-window.c

@@ -149,7 +149,7 @@ cmd_split_window_exec(struct cmd *self, struct cmd_ctx *ctx)
 	struct winlink			*wl;
 	struct window			*w;
 	struct window_pane		*wp;
-	const char		       **env;
+	struct environ			 env;
 	char		 		*cmd, *cwd, *cause;
 	u_int				 hlimit;
 	int				 size;
@@ -159,7 +159,10 @@ cmd_split_window_exec(struct cmd *self, struct cmd_ctx *ctx)
 		return (-1);
 	w = wl->window;
 
-	env = server_fill_environ(s);
+	environ_init(&env);
+	environ_copy(&global_environ, &env);
+	environ_copy(&s->environ, &env);
+	server_fill_environ(s, &env);
 
 	cmd = data->cmd;
 	if (cmd == NULL)
@@ -181,7 +184,7 @@ cmd_split_window_exec(struct cmd *self, struct cmd_ctx *ctx)
 		type = LAYOUT_LEFTRIGHT;
 
 	wp = window_add_pane(w, hlimit);
-	if (window_pane_spawn(wp, cmd, cwd, env, &cause) != 0)
+	if (window_pane_spawn(wp, cmd, cwd, &env, &cause) != 0)
 		goto error;
 	if (layout_split_pane(w->active, type, size, wp) != 0) {
 		cause = xstrdup("pane too small");
@@ -197,9 +200,11 @@ cmd_split_window_exec(struct cmd *self, struct cmd_ctx *ctx)
 	} else
 		server_status_session(s);
 
+	environ_free(&env);
 	return (0);
 
 error:
+	environ_free(&env);
 	if (wp != NULL)
 		window_remove_pane(w, wp);
 	ctx->error(ctx, "create pane failed: %s", cause);

cmd-string.c

@@ -59,21 +59,11 @@ int
 cmd_string_parse(const char *s, struct cmd_list **cmdlist, char **cause)
 {
 	size_t		p;
-	int		ch, argc, rval, have_arg;
+	int		ch, i, argc, rval, have_arg;
-	char	      **argv, *buf, *t, *u;
+	char	      **argv, *buf, *t;
+	const char     *whitespace, *equals;
 	size_t		len;
 
-	if ((t = strchr(s, ' ')) == NULL && (t = strchr(s, '\t')) == NULL)
-		t = strchr(s, '\0');
-	if ((u = strchr(s, '=')) != NULL && u < t) {
-		if (putenv(xstrdup(s)) != 0) {
-			xasprintf(cause, "assignment failed: %s", s);
-			return (-1);
-		}
-		*cmdlist = NULL;
-		return (0);
-	}
-
 	argv = NULL;
 	argc = 0;
 
@@ -147,6 +137,18 @@ cmd_string_parse(const char *s, struct cmd_list **cmdlist, char **cause)
 			if (argc == 0)
 				goto out;
 
+			for (i = 0; i < argc; i++) {
+				equals = strchr(argv[i], '=');
+				whitespace = argv[i] + strcspn(argv[i], " \t");
+				if (equals == NULL || equals > whitespace)
+					break;
+				environ_put(&global_environ, argv[i]);
+				memmove(&argv[i], &argv[i + 1], argc - i - 1);
+				argc--;
+			}
+			if (argc == 0)
+				goto out;
+
 			*cmdlist = cmd_list_parse(argc, argv, cause);
 			if (*cmdlist == NULL)
 				goto out;

cmd.c

@@ -84,10 +84,12 @@ const struct cmd_entry *cmd_table[] = {
 	&cmd_send_prefix_entry,
 	&cmd_server_info_entry,
 	&cmd_set_buffer_entry,
+	&cmd_set_environment_entry,
 	&cmd_set_option_entry,
 	&cmd_set_password_entry,
 	&cmd_set_window_option_entry,
 	&cmd_show_buffer_entry,
+	&cmd_show_environment_entry,
 	&cmd_show_options_entry,
 	&cmd_show_window_options_entry,
 	&cmd_source_file_entry,

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);
+}

server-fn.c

@@ -26,25 +26,20 @@
 
 int	server_lock_callback(void *, const char *);
 
-const char **
+void
-server_fill_environ(struct session *s)
+server_fill_environ(struct session *s, struct environ *env)
 {
-	static const char *env[] = { NULL /* TMUX= */, NULL /* TERM */, NULL };
+	char		 tmuxvar[MAXPATHLEN], *term;
-	static char	tmuxvar[MAXPATHLEN + 256], termvar[256];
+	u_int		 idx;
-	u_int		idx;
 
 	if (session_index(s, &idx) != 0)
 		fatalx("session not found");
-
 	xsnprintf(tmuxvar, sizeof tmuxvar,
-	    "TMUX=%s,%ld,%u", socket_path, (long) getpid(), idx);
+	    "%s,%ld,%u", socket_path, (long) getpid(), idx);
-	env[0] = tmuxvar;
+	environ_set(env, "TMUX", tmuxvar);
 
-	xsnprintf(termvar, sizeof termvar,
+	term = options_get_string(&s->options, "default-terminal");
-	    "TERM=%s", options_get_string(&s->options, "default-terminal"));
+	environ_set(env, "TERM", term);
-	env[1] = termvar;
-
-	return (env);
 }
 
 void

server-msg.c

@@ -42,6 +42,7 @@ server_msg_dispatch(struct client *c)
 	struct msg_identify_data identifydata;
 	struct msg_resize_data	 resizedata;
 	struct msg_unlock_data	 unlockdata;
+	struct msg_environ_data	 environdata;
 
 	for (;;) {
 		if (BUFFER_USED(c->in) < sizeof hdr)
@@ -100,6 +101,15 @@ server_msg_dispatch(struct client *c)
 			tty_start_tty(&c->tty);
 			server_redraw_client(c);
 			break;
+		case MSG_ENVIRON:
+			if (hdr.size != sizeof environdata)
+				fatalx("bad MSG_ENVIRON size");
+			buffer_read(c->in, &environdata, sizeof environdata);
+
+			environdata.var[(sizeof environdata.var) - 1] = '\0';
+			if (strchr(environdata.var, '=') != NULL)
+				environ_put(&c->environ, environdata.var);
+			break;
 		default:
 			fatalx("unexpected message");
 		}

session.c

@@ -112,8 +112,8 @@ session_find(const char *name)
 
 /* Create a new session. */
 struct session *
-session_create(const char *name,
+session_create(const char *name, const char *cmd, const char *cwd,
-    const char *cmd, const char *cwd, u_int sx, u_int sy, char **cause)
+    struct environ *env, u_int sx, u_int sy, char **cause)
 {
 	struct session	*s;
 	u_int		 i;
@@ -128,6 +128,9 @@ session_create(const char *name,
 	SLIST_INIT(&s->alerts);
 	paste_init_stack(&s->buffers);
 	options_init(&s->options, &global_s_options);
+	environ_init(&s->environ);
+	if (env != NULL)
+		environ_copy(env, &s->environ);
 
 	s->sx = sx;
 	s->sy = sy;
@@ -171,6 +174,7 @@ session_destroy(struct session *s)
 		ARRAY_TRUNC(&sessions, 1);
 
 	session_alert_cancel(s, NULL);
+	environ_free(&s->environ);
 	options_free(&s->options);
 	paste_free_stack(&s->buffers);
 
@@ -200,15 +204,21 @@ session_new(struct session *s,
     const char *name, const char *cmd, const char *cwd, int idx, char **cause)
 {
 	struct window	*w;
-	const char     **env;
+	struct environ	 env;
 	u_int		 hlimit;
 
-	env = server_fill_environ(s);
+	environ_init(&env);
+	environ_copy(&global_environ, &env);
+	environ_copy(&s->environ, &env);
+	server_fill_environ(s, &env);
 
 	hlimit = options_get_number(&s->options, "history-limit");
-	w = window_create(name, cmd, cwd, env, s->sx, s->sy, hlimit, cause);
+	w = window_create(name, cmd, cwd, &env, s->sx, s->sy, hlimit, cause);
-	if (w == NULL)
+	if (w == NULL) {
+		environ_free(&env);
 		return (NULL);
+	}
+	environ_free(&env);
 
 	if (options_get_number(&s->options, "set-remain-on-exit"))
 		options_set_number(&w->options, "remain-on-exit", 1);

tmux.1

@@ -1321,6 +1321,18 @@ entry for terminals which support 88 or 256 colours:
 .Bd -literal -offset indent
 "*88col*:colors=88,*256col*:colors=256"
 .Ed
+.It Ic update-environment Ar variables
+Set a space-separated string containing a list of environment variables to be
+copied into the session environment when a new session is created or an
+existing session is attached.
+Any variables that do not exist in the source environment are set to be
+removed from the session environment (as if
+.Fl r
+was given to the
+.Ic set-environment
+command).
+The default is
+.Ev DISPLAY .
 .It Xo Ic visual-activity
 .Op Ic on | off
 .Xc
@@ -1525,6 +1537,60 @@ or the global window options if
 .Fl g
 is used.
 .El
+.Sh ENVIRONMENT
+When the server is started,
+.Nm
+copies the environment into the
+.Em global environment ;
+in addition, each session has a
+.Em session environment .
+When a window is created, the session and global environments are merged with
+the session environment overriding any variable present in both.
+This is the initial environment passed to the new process.
+.Pp
+The
+.Ic update-environment
+session option may be used to update the session environment from the client
+when a new session is created or an old reattached.
+.Nm
+also initialises the
+.Ev TMUX
+variable with some internal information to allow commands to be executed
+from inside, and the
+.Ev TERM
+variable with the correct terminal setting of
+.Ql screen .
+.Pp
+Commands to alter and view the environment are:
+.Bl -tag -width Ds
+.It Xo Ic set-environment
+.Op Fl gru
+.Op Fl t Ar target-session
+.Ar name Op Ar value
+.Xc
+Set or unset an environment variable.
+If
+.Fl g
+is used, the change is made in the global environment; otherwise, it is applied
+to the session environment for
+.Ar target-session .
+The
+.Fl u
+flag unsets a variable.
+.Fl r
+indicates the variable is to be removed from the environment before starting a
+new process.
+.It Xo Ic show-environment
+.Op Fl g
+.Op Fl t Ar target-session
+.Xc
+Display the environment for
+.Ar target-session
+or the global environment with
+.Fl g .
+Variables removed from the environment are prefixed with
+.Ql - .
+.El
 .Sh STATUS LINE
 .Nm
 includes an optional status line which is displayed in the bottom line of each

tmux.c

@@ -44,6 +44,7 @@ volatile sig_atomic_t sigusr2;
 char		*cfg_file;
 struct options	 global_s_options;	/* session options */
 struct options	 global_w_options;	/* window options */
+struct environ	 global_environ;
 
 int		 server_locked;
 u_int		 password_failures;
@@ -262,7 +263,7 @@ main(int argc, char **argv)
 	struct hdr	 	 hdr;
 	struct passwd		*pw;
 	struct msg_print_data	 printdata;
-	char			*s, *path, *label, *home, *cause;
+	char			*s, *path, *label, *home, *cause, **var;
 	char			 cwd[MAXPATHLEN];
 	void			*buf;
 	size_t			 len;
@@ -320,6 +321,10 @@ main(int argc, char **argv)
 	log_open_tty(debug_level);
 	siginit();
 
+	environ_init(&global_environ);
+ 	for (var = environ; *var != NULL; var++)
+		environ_put(&global_environ, *var);
+
 	if (!(flags & IDENTIFY_UTF8)) {
 		/*
 		 * If the user has set whichever of LC_ALL, LC_CTYPE or LANG
@@ -376,6 +381,7 @@ main(int argc, char **argv)
 		options_set_number(&global_s_options, "status-utf8", 0);
 	options_set_string(&global_s_options,
 	    "terminal-overrides", "*88col*:colors=88,*256col*:colors=256");
+	options_set_string(&global_s_options, "update-environment", "DISPLAY");
 	options_set_number(&global_s_options, "visual-activity", 0);
 	options_set_number(&global_s_options, "visual-bell", 0);
 	options_set_number(&global_s_options, "visual-content", 0);
@@ -469,10 +475,10 @@ main(int argc, char **argv)
 		}
 		cmdflags &= ~CMD_STARTSERVER;
 		TAILQ_FOREACH(cmd, cmdlist, qentry) {
-			if (cmd->entry->flags & CMD_STARTSERVER) {
+			if (cmd->entry->flags & CMD_STARTSERVER)
 				cmdflags |= CMD_STARTSERVER;
-				break;
+			if (cmd->entry->flags & CMD_SENDENVIRON)
-			}
+				cmdflags |= CMD_SENDENVIRON;
 		}
 		cmd_list_free(cmdlist);
 	}

tmux.h

@@ -39,6 +39,7 @@
 #include "array.h"
 
 extern char    *__progname;
+extern char   **environ;
 
 /* Default configuration files. */
 #define DEFAULT_CFG ".tmux.conf"
@@ -69,6 +70,7 @@ extern char    *__progname;
 #define COMMAND_LENGTH 2048	/* packed argv size */
 #define TERMINAL_LENGTH 128	/* length of TERM environment variable */
 #define PRINT_LENGTH 512	/* printed error/message size */
+#define ENVIRON_LENGTH 1024	/* environment variable length */
 
 /* Fatal errors. */
 #define fatal(msg) log_fatal("%s: %s", __func__, msg);
@@ -302,6 +304,7 @@ enum msgtype {
 	MSG_SUSPEND,
 	MSG_UNLOCK,
 	MSG_WAKEUP,
+	MSG_ENVIRON
 };
 
 /*
@@ -356,6 +359,10 @@ struct msg_unlock_data {
 	char	       	pass[PASS_MAX];
 };
 
+struct msg_environ_data {
+	char	     	var[ENVIRON_LENGTH];
+};
+
 /* Mode key commands. */
 enum mode_key_cmd {
 	MODEKEY_NONE,
@@ -765,6 +772,15 @@ struct paste_buffer {
 };
 ARRAY_DECL(paste_stack, struct paste_buffer *);
 
+/* Environment variable. */
+struct environ_entry {
+	char		*name;
+	char		*value;
+
+	RB_ENTRY(environ_entry) entry;
+};
+RB_HEAD(environ, environ_entry);
+
 /* Client session. */
 struct session_alert {
 	struct winlink	*wl;
@@ -792,6 +808,8 @@ struct session {
 
 #define SESSION_UNATTACHED 0x1	/* not attached to any clients */
 	int		 flags;
+
+	struct environ	 environ;
 };
 ARRAY_DECL(sessions, struct session *);
 
@@ -894,6 +912,8 @@ struct client {
 	struct buffer	*in;
 	struct buffer	*out;
 
+	struct environ	 environ;
+
 	char		*title;
 	char		*cwd;
 
@@ -992,6 +1012,7 @@ struct cmd_entry {
 #define CMD_CANTNEST 0x2
 #define CMD_ARG1 0x4
 #define CMD_ARG01 0x8
+#define CMD_SENDENVIRON 0x10
 	int		 flags;
 
 #define CMD_CHFLAG(flag) \
@@ -1074,6 +1095,7 @@ extern volatile sig_atomic_t sigusr1;
 extern volatile sig_atomic_t sigusr2;
 extern struct options global_s_options;
 extern struct options global_w_options;
+extern struct environ global_environ;
 extern char	*cfg_file;
 extern int	 server_locked;
 extern u_int	 password_failures;
@@ -1123,6 +1145,18 @@ char   *options_get_string(struct options *, const char *);
 void	options_set_number(struct options *, const char *, long long);
 long long options_get_number(struct options *, const char *);
 
+/* environ.c */
+int	environ_cmp(struct environ_entry *, struct environ_entry *);
+RB_PROTOTYPE(environ, environ_entry, entry, environ_cmp);
+void	environ_init(struct environ *);
+void	environ_free(struct environ *);
+void	environ_copy(struct environ *, struct environ *);
+struct environ_entry *environ_find(struct environ *, const char *);
+void	environ_set(struct environ *, const char *, const char *);
+void	environ_put(struct environ *, const char *);
+void	environ_unset(struct environ *, const char *);
+void 	environ_update(const char *, struct environ *, struct environ *);
+
 /* tty.c */
 u_char	tty_get_acs(struct tty *, u_char);
 void	tty_reset(struct tty *);
@@ -1285,10 +1319,12 @@ extern const struct cmd_entry cmd_send_keys_entry;
 extern const struct cmd_entry cmd_send_prefix_entry;
 extern const struct cmd_entry cmd_server_info_entry;
 extern const struct cmd_entry cmd_set_buffer_entry;
+extern const struct cmd_entry cmd_set_environment_entry;
 extern const struct cmd_entry cmd_set_option_entry;
 extern const struct cmd_entry cmd_set_password_entry;
 extern const struct cmd_entry cmd_set_window_option_entry;
 extern const struct cmd_entry cmd_show_buffer_entry;
+extern const struct cmd_entry cmd_show_environment_entry;
 extern const struct cmd_entry cmd_show_options_entry;
 extern const struct cmd_entry cmd_show_window_options_entry;
 extern const struct cmd_entry cmd_source_file_entry;
@@ -1384,7 +1420,7 @@ int	 server_start(char *);
 int	 server_msg_dispatch(struct client *);
 
 /* server-fn.c */
-const char **server_fill_environ(struct session *);
+void	 server_fill_environ(struct session *, struct environ *);
 void	 server_write_error(struct client *, const char *);
 void	 server_write_client(
              struct client *, enum msgtype, const void *, size_t);
@@ -1554,8 +1590,8 @@ void		 winlink_stack_push(struct winlink_stack *, struct winlink *);
 void		 winlink_stack_remove(struct winlink_stack *, struct winlink *);
 int	 	 window_index(struct window *, u_int *);
 struct window	*window_create1(u_int, u_int);
-struct window	*window_create(const char *, const char *,
+struct window	*window_create(const char *, const char *, const char *,
-		     const char *, const char **, u_int, u_int, u_int, char **);
+    		     struct environ *, u_int, u_int, u_int, char **);
 void		 window_destroy(struct window *);
 void		 window_set_active_pane(struct window *, struct window_pane *);
 struct window_pane *window_add_pane(struct window *, u_int);
@@ -1568,7 +1604,7 @@ void		 window_destroy_panes(struct window *);
 struct window_pane *window_pane_create(struct window *, u_int, u_int, u_int);
 void		 window_pane_destroy(struct window_pane *);
 int		 window_pane_spawn(struct window_pane *,
-		     const char *, const char *, const char **, char **);
+		     const char *, const char *, struct environ *, char **);
 void		 window_pane_resize(struct window_pane *, u_int, u_int);
 int		 window_pane_set_mode(
 		     struct window_pane *, const struct window_mode *);
@@ -1648,7 +1684,7 @@ int	 session_alert_has(struct session *, struct winlink *, int);
 int	 session_alert_has_window(struct session *, struct window *, int);
 struct session	*session_find(const char *);
 struct session	*session_create(const char *, const char *,
-    		     const char *, u_int, u_int, char **);
+    		     const char *, struct environ *, u_int, u_int, char **);
 void	 	 session_destroy(struct session *);
 int	 	 session_index(struct session *, u_int *);
 struct winlink	*session_new(struct session *,

window.c

@@ -254,7 +254,7 @@ window_create1(u_int sx, u_int sy)
 
 struct window *
 window_create(const char *name, const char *cmd, const char *cwd,
-    const char **envp, u_int sx, u_int sy, u_int hlimit, char **cause)
+    struct environ *env, u_int sx, u_int sy, u_int hlimit, char **cause)
 {
 	struct window		*w;
 	struct window_pane	*wp;
@@ -262,7 +262,7 @@ window_create(const char *name, const char *cmd, const char *cwd,
 	w = window_create1(sx, sy);
 	wp = window_add_pane(w, hlimit);
 	layout_init(w);
-	if (window_pane_spawn(wp, cmd, cwd, envp, cause) != 0) {
+	if (window_pane_spawn(wp, cmd, cwd, env, cause) != 0) {
 		window_destroy(w);
 		return (NULL);
 	}
@@ -456,13 +456,16 @@ window_pane_destroy(struct window_pane *wp)
 
 int
 window_pane_spawn(struct window_pane *wp,
-    const char *cmd, const char *cwd, const char **envp, char **cause)
+    const char *cmd, const char *cwd, struct environ *env, char **cause)
 {
-	struct winsize	 ws;
+	struct winsize	 	 ws;
-	int		 mode;
+	int		 	 mode;
-	const char     **envq, *ptr;
+	char			*argv0, **varp, *var;
-	char		*argv0;
+	ARRAY_DECL(, char *)	 varlist;
-	struct timeval	 tv;
+	struct environ_entry	*envent;
+	const char		*ptr;
+	struct timeval	 	 tv;
+	u_int		 	 i;
 
 	if (wp->fd != -1)
 		close(wp->fd);
@@ -495,10 +498,22 @@ window_pane_spawn(struct window_pane *wp,
 	case 0:
 		if (chdir(wp->cwd) != 0)
 			chdir("/");
-		for (envq = envp; *envq != NULL; envq++) {
+
-			if (putenv(xstrdup(*envq)) != 0)
+		ARRAY_INIT(&varlist);
-				fatal("putenv failed");
+		for (varp = environ; *varp != NULL; varp++) {
+			var = xstrdup(*varp);
+			var[strcspn(var, "=")] = '\0';
+			ARRAY_ADD(&varlist, var);
 		}
+		for (i = 0; i < ARRAY_LENGTH(&varlist); i++) {
+			var = ARRAY_ITEM(&varlist, i);
+			unsetenv(var);
+		}
+		RB_FOREACH(envent, environ, env) {
+			if (envent->value != NULL)
+				setenv(envent->name, envent->value, 1);
+		}
+
 		sigreset();
 		log_close();