Add a -s flag to show-environment to output Bourne shell commands a la

ssh-agent. Mostly from Cam Hutchison with some changes by me.

cmd-show-environment.c

@@ -27,16 +27,61 @@
  * Show environment.
  */
 
-enum cmd_retval	 cmd_show_environment_exec(struct cmd *, struct cmd_q *);
+enum cmd_retval	cmd_show_environment_exec(struct cmd *, struct cmd_q *);
+
+char	*cmd_show_environment_escape(struct environ_entry *);
+void	 cmd_show_environment_print(struct cmd *, struct cmd_q *,
+	     struct environ_entry *);
 
 const struct cmd_entry cmd_show_environment_entry = {
 	"show-environment", "showenv",
-	"gt:", 0, 1,
+	"gst:", 0, 1,
-	"[-g] " CMD_TARGET_SESSION_USAGE " [name]",
+	"[-gs] " CMD_TARGET_SESSION_USAGE " [name]",
 	0,
 	cmd_show_environment_exec
 };
 
+char *
+cmd_show_environment_escape(struct environ_entry *envent)
+{
+	const char	*value = envent->value;
+	char		 c, *out, *ret;
+
+	out = ret = xmalloc(strlen(value) * 2 + 1); /* at most twice the size */
+	while ((c = *value++) != '\0') {
+		/* POSIX interprets $ ` " and \ in double quotes. */
+		if (c == '$' || c == '`' || c == '"' || c == '\\')
+			*out++ = '\\';
+		*out++ = c;
+	}
+	*out = '\0';
+
+	return ret;
+}
+
+void
+cmd_show_environment_print(struct cmd *self, struct cmd_q *cmdq,
+    struct environ_entry *envent)
+{
+	char	*escaped;
+
+	if (!args_has(self->args, 's')) {
+		if (envent->value != NULL)
+			cmdq_print(cmdq, "%s=%s", envent->name, envent->value);
+		else
+			cmdq_print(cmdq, "-%s", envent->name);
+		return;
+	}
+
+	if (envent->value != NULL) {
+		escaped = cmd_show_environment_escape(envent);
+		cmdq_print(cmdq, "%s=\"%s\"; export %s;", envent->name, escaped,
+		    envent->name);
+		free(escaped);
+	} else
+		cmdq_print(cmdq, "unset %s;", envent->name);
+}
+
 enum cmd_retval
 cmd_show_environment_exec(struct cmd *self, struct cmd_q *cmdq)
 {
@@ -48,7 +93,8 @@ cmd_show_environment_exec(struct cmd *self, struct cmd_q *cmdq)
 	if (args_has(self->args, 'g'))
 		env = &global_environ;
 	else {
-		if ((s = cmd_find_session(cmdq, args_get(args, 't'), 0)) == NULL)
+		s = cmd_find_session(cmdq, args_get(args, 't'), 0);
+		if (s == NULL)
 			return (CMD_RETURN_ERROR);
 		env = &s->environ;
 	}
@@ -59,19 +105,11 @@ cmd_show_environment_exec(struct cmd *self, struct cmd_q *cmdq)
 			cmdq_error(cmdq, "unknown variable: %s", args->argv[0]);
 			return (CMD_RETURN_ERROR);
 		}
-		if (envent->value != NULL)
+		cmd_show_environment_print(self, cmdq, envent);
-			cmdq_print(cmdq, "%s=%s", envent->name, envent->value);
-		else
-			cmdq_print(cmdq, "-%s", envent->name);
 		return (CMD_RETURN_NORMAL);
 	}
 
-	RB_FOREACH(envent, environ, env) {
+	RB_FOREACH(envent, environ, env)
-		if (envent->value != NULL)
+		cmd_show_environment_print(self, cmdq, envent);
-			cmdq_print(cmdq, "%s=%s", envent->name, envent->value);
-		else
-			cmdq_print(cmdq, "-%s", envent->name);
-	}
-
 	return (CMD_RETURN_NORMAL);
 }

tmux.1

@@ -3542,7 +3542,7 @@ flag unsets a variable.
 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 gs
 .Op Fl t Ar target-session
 .Op Ar variable
 .Xc
@@ -3556,6 +3556,9 @@ If
 is omitted, all variables are shown.
 Variables removed from the environment are prefixed with
 .Ql - .
+If
+.Fl s
+is used, the output is formatted as a set of Bourne shell commands.
 .El
 .Sh STATUS LINE
 .Nm