+/*
+ * Built-in functions
+ */
+struct function {
+ const char *name;
+ unsigned int min_args;
+ unsigned int max_args;
+ char *(*func)(int argc, char *argv[]);
+};
+
+static char *do_shell(int argc, char *argv[])
+{
+ FILE *p;
+ char buf[256];
+ char *cmd;
+ size_t nread;
+ int i;
+
+ cmd = argv[0];
+
+ p = popen(cmd, "r");
+ if (!p) {
+ perror(cmd);
+ exit(1);
+ }
+
+ nread = fread(buf, 1, sizeof(buf), p);
+ if (nread == sizeof(buf))
+ nread--;
+
+ /* remove trailing new lines */
+ while (buf[nread - 1] == '\n')
+ nread--;
+
+ buf[nread] = 0;
+
+ /* replace a new line with a space */
+ for (i = 0; i < nread; i++) {
+ if (buf[i] == '\n')
+ buf[i] = ' ';
+ }
+
+ if (pclose(p) == -1) {
+ perror(cmd);
+ exit(1);
+ }
+
+ return xstrdup(buf);
+}
+
+static const struct function function_table[] = {
+ /* Name MIN MAX Function */
+ { "shell", 1, 1, do_shell },
+};
+
+#define FUNCTION_MAX_ARGS 16
+
+static char *function_expand(const char *name, int argc, char *argv[])
+{
+ const struct function *f;
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(function_table); i++) {
+ f = &function_table[i];
+ if (strcmp(f->name, name))
+ continue;
+
+ if (argc < f->min_args)
+ pperror("too few function arguments passed to '%s'",
+ name);
+
+ if (argc > f->max_args)
+ pperror("too many function arguments passed to '%s'",
+ name);
+
+ return f->func(argc, argv);
+ }
+
+ return NULL;
+}
+
+/*
+ * Variables (and user-defined functions)
+ */
+static LIST_HEAD(variable_list);
+
+struct variable {
+ char *name;
+ char *value;
+ struct list_head node;
+};
+
+static struct variable *variable_lookup(const char *name)
+{
+ struct variable *v;
+
+ list_for_each_entry(v, &variable_list, node) {
+ if (!strcmp(name, v->name))
+ return v;
+ }
+
+ return NULL;
+}
+
+static char *variable_expand(const char *name, int argc, char *argv[])
+{
+ struct variable *v;
+
+ v = variable_lookup(name);
+ if (!v)
+ return NULL;
+
+ return expand_string_with_args(v->value, argc, argv);
+}
+
+void variable_add(const char *name, const char *value)
+{
+ struct variable *v;
+
+ v = variable_lookup(name);
+ if (v) {
+ free(v->value);
+ } else {
+ v = xmalloc(sizeof(*v));
+ v->name = xstrdup(name);
+ list_add_tail(&v->node, &variable_list);
+ }
+
+ v->value = xstrdup(value);
+}
+
+static void variable_del(struct variable *v)
+{
+ list_del(&v->node);
+ free(v->name);
+ free(v->value);
+ free(v);
+}
+
+void variable_all_del(void)