SP
...
if ((config_val = ast_variable_retrieve(member_config, category, realtime_ringinuse_field))) {
if (ast_true(config_val)) {
ringinuse = 1;
} else if (ast_false(config_val)) {
ringinuse = 0;
} else {
ast_log(LOG_WARNING, "Invalid value of '%s' field for %s in queue '%s'\n", realtime_ringinuse_field, interface, q->name);
}
}
...
А ast_true и ast_false переваривают соответственно "yes"/"no", "true"/"false", "y"/"n", "t"/"f" и "1"/"0"