refactor(script): Split non-/tail logic

Split the script module into one tailing output module and
one exec once module.

Refs #281

src/modules/tailscript.cpp

@@ -0,0 +1,50 @@
+#include "modules/tailscript.hpp"
+#include "drawtypes/label.hpp"
+
+#include "modules/meta/base.inl"
+
+POLYBAR_NS
+
+namespace modules {
+  tailscript_module::tailscript_module(const bar_settings& bar, string name_) : script_module(bar, move(name_)) {
+    m_interval = m_conf.get<decltype(m_interval)>(name(), "interval", 0s);
+  }
+
+  void tailscript_module::process() {
+    if (!m_updatelock.try_lock()) {
+      return;
+    }
+
+    std::unique_lock<mutex> guard(m_updatelock, std::adopt_lock);
+
+    if (!m_command || !m_command->is_running()) {
+      string exec{string_util::replace_all(m_exec, "%counter%", to_string(++m_counter))};
+      m_log.info("%s: Invoking shell command: \"%s\"", name(), exec);
+      m_command = command_util::make_command(exec);
+
+      try {
+        m_command->exec(false);
+      } catch (const exception& err) {
+        m_log.err("%s: %s", name(), err.what());
+        throw module_error("Failed to execute command, stopping module...");
+      }
+    }
+
+    if (io_util::poll(m_command->get_stdout(PIPE_READ), POLLIN, 0)) {
+      if ((m_output = m_command->readline()) != m_prev) {
+        m_prev = m_output;
+        broadcast();
+      }
+    }
+
+    guard.unlock();
+
+    if (m_command && !m_command->is_running()) {
+      sleep(std::max(m_command->get_exit_status() == 0 ? m_interval : 1s, m_interval));
+    } else {
+      sleep(m_interval);
+    }
+  }
+}
+
+POLYBAR_NS_END