feat(ipc): Add polybar-msg to facilitate ipc messaging

build.sh

@@ -28,6 +28,7 @@ function main
   mkdir ./build || msg_err "Failed to create build dir"
   cd ./build || msg_err "Failed to enter build dir"
 
+  local build_ipc_msg="ON"
   local enable_alsa="ON"
   local enable_i3="ON"
   local enable_network="ON"
@@ -46,6 +47,8 @@ function main
   [[ "${p^^}" != "Y" ]] && enable_mpd="OFF"
   read -r -p "$(msg "Include support for \"internal/github\" (requires libcurl) ---------- [Y/n]: ")" -n 1 p && echo
   [[ "${p^^}" != "Y" ]] && enable_curl="OFF"
+  read -r -p "$(msg "Build \"polybar-msg\" used to send ipc messages --------------------- [Y/n]: ")" -n 1 p && echo
+  [[ "${p^^}" != "Y" ]] && build_ipc_msg="OFF"
 
   local cxx="c++"
   local cc="cc"
@@ -69,6 +72,7 @@ function main
     -DENABLE_MPD:BOOL="${enable_mpd}"         \
     -DENABLE_NETWORK:BOOL="${enable_network}" \
     -DENABLE_CURL:BOOL="${enable_curl}"       \
+    -DBUILD_IPC_MSG:BOOL="${build_ipc_msg}"   \
     .. || msg_err "Failed to generate build... read output to get a hint of what went wrong"
 
   msg "Building project"

cmake/build/options.cmake

@@ -48,6 +48,7 @@ endif()
 option(CXXLIB_CLANG       "Link against libc++"        OFF)
 option(CXXLIB_GCC         "Link against stdlibc++"     OFF)
 
+option(BUILD_IPC_MSG      "Build ipc messager"         ON)
 option(BUILD_TESTS        "Build testsuite"            OFF)
 option(DEBUG_LOGGER       "Enable extra debug logging" OFF)
 option(VERBOSE_TRACELOG   "Enable verbose trace logs"  OFF)

cmake/build/summary.cmake

@@ -53,6 +53,7 @@ else()
 endif()
 
 message(STATUS "--------------------------")
+colored_option(STATUS " Build polybar-msg    ${BUILD_IPC_MSG}" BUILD_IPC_MSG "32;1" "37;2")
 colored_option(STATUS " Build testsuite      ${BUILD_TESTS}" BUILD_TESTS "32;1" "37;2")
 colored_option(STATUS " Debug logging        ${DEBUG_LOGGER}" DEBUG_LOGGER "32;1" "37;2")
 colored_option(STATUS " Verbose tracing      ${VERBOSE_TRACELOG}" VERBOSE_TRACELOG "32;1" "37;2")

include/utils/file.hpp

@@ -102,6 +102,7 @@ namespace file_util {
   string pick(const vector<string>& filenames);
   string contents(const string& filename);
   bool is_fifo(const string& filename);
+  vector<string> glob(const string& pattern);
 
   template <typename... Args>
   decltype(auto) make_file_descriptor(Args&&... args) {

src/CMakeLists.txt

@@ -3,6 +3,7 @@
 #
 
 file(GLOB_RECURSE SOURCES RELATIVE ${PROJECT_SOURCE_DIR}/src *.c[p]*)
+list(REMOVE_ITEM SOURCES ipc.cpp)
 
 # Locate dependencies {{{
 
@@ -142,14 +143,18 @@ target_compile_definitions(${PROJECT_NAME} PUBLIC
   ${XCB_DEFINITIONS})
 
 # }}}
-# Export target details {{{
+# Create executable target: ipc messager {{{
+
+if(BUILD_IPC_MSG)
+  make_executable(${PROJECT_NAME}-msg SOURCES ipc.cpp utils/file.cpp)
+endif()
+
+# }}}
 
 set(APP_BINARY ${PROJECT_SOURCE_DIR}/bin/${PROJECT_NAME} PARENT_SCOPE)
 set(APP_LIBRARIES ${APP_LIBRARIES} PARENT_SCOPE)
 set(APP_INCLUDE_DIRS ${APP_INCLUDE_DIRS} PARENT_SCOPE)
 
-# }}}
-
 execute_process(COMMAND git describe --tags --dirty=-git
   WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}
   OUTPUT_VARIABLE APP_VERSION

src/ipc.cpp

@@ -0,0 +1,126 @@
+#include <fcntl.h>
+#include <algorithm>
+#include <cstring>
+#include <iostream>
+#include <vector>
+
+#include "common.hpp"
+#include "utils/file.hpp"
+
+using namespace polybar;
+
+void log(const string& msg) {
+  std::cerr << "polybar-msg: " << msg << std::endl;
+}
+
+void log(int exit_code, const string& msg) {
+  std::cerr << "polybar-msg: " << msg << std::endl;
+  exit(exit_code);
+}
+
+void usage(const string& parameters) {
+  std::cerr << "Usage: polybar-msg [-p pid] " << parameters << std::endl;
+  exit(127);
+}
+
+bool validate_type(const string& type) {
+  if (type == "action") {
+    return true;
+  } else if (type == "cmd") {
+    return true;
+  } else if (type == "hook") {
+    return true;
+  } else {
+    return false;
+  }
+}
+
+int main(int argc, char** argv) {
+  const int E_GENERIC{1};
+  const int E_NO_CHANNELS{2};
+  const int E_MESSAGE_TYPE{3};
+  const int E_INVALID_PID{4};
+  const int E_INVALID_CHANNEL{5};
+  const int E_WRITE{6};
+
+  vector<string> args{argv + 1, argv + argc};
+  string::size_type p;
+  int pid{0};
+
+  // If -p <pid> is passed, check if the process is running and that
+  // a valid channel pipe is available
+  if (args.size() >= 2 && args[0].compare(0, 2, "-p") == 0) {
+    if (!file_util::exists("/proc/" + args[1])) {
+      log(E_INVALID_PID, "No process with pid " + args[1]);
+    } else if (!file_util::is_fifo("/tmp/polybar_mqueue." + args[1])) {
+      log(E_INVALID_CHANNEL, "No channel available for pid " + args[1]);
+    }
+
+    pid = std::atoi(args[1].c_str());
+    args.erase(args.begin());
+    args.erase(args.begin());
+  }
+
+  // Validate args
+  if (args.size() < 2) {
+    usage("<command=(action|cmd|hook)> <payload> [...]");
+  } else if (!validate_type(args[0])) {
+    log(E_MESSAGE_TYPE, "\"" + args[0] + "\" is not a valid type.");
+  }
+
+  string ipc_type{args[0]};
+  args.erase(args.begin());
+  string ipc_payload{args[0]};
+  args.erase(args.begin());
+
+  // Check hook specific args
+  if (ipc_type == "hook") {
+    if (args.size() != 1) {
+      usage("hook <module-name> <hook-index>");
+    } else if ((p = ipc_payload.find("module/")) != 0) {
+      ipc_payload = "module/" + ipc_payload + args[0];
+      args.erase(args.begin());
+    } else {
+      ipc_payload += args[0];
+      args.erase(args.begin());
+    }
+  }
+
+  // Get availble channel pipes
+  auto channels = file_util::glob("/tmp/polybar_mqueue.*");
+  if (channels.empty()) {
+    log(E_NO_CHANNELS, "There are no active ipc channels");
+  }
+
+  // Write the message to each channel in the list and remove stale
+  // channel pipes that may be left lingering if the owning process got
+  // SIGKILLED or crashed
+  for (auto&& channel : channels) {
+    string handle{channel};
+    int handle_pid{0};
+
+    if ((p = handle.rfind('.')) != string::npos) {
+      handle_pid = std::atoi(handle.substr(p + 1).c_str());
+    }
+
+    if (!file_util::exists("/proc/" + to_string(handle_pid))) {
+      if (unlink(handle.c_str()) == -1) {
+        log(E_GENERIC, "Could not remove stale ipc channel: " + string{std::strerror(errno)});
+      } else {
+        log("Removed stale ipc channel: " + handle);
+      }
+    } else if (!pid || pid == handle_pid) {
+      string payload{ipc_type + ":" + ipc_payload};
+
+      try {
+        fd_stream<std::ostream> out(handle, O_WRONLY);
+        out << payload << '\n';
+        log("Successfully wrote \"" + payload + "\" to \"" + handle + "\"");
+      } catch (const std::exception& err) {
+        log(E_WRITE, "Failed to write \"" + payload + "\" to \"" + handle + "\" (err: " + err.what() + ")");
+      }
+    }
+  }
+
+  return 0;
+}

src/utils/file.cpp

@@ -1,4 +1,5 @@
 #include <fcntl.h>
+#include <glob.h>
 #include <sys/stat.h>
 #include <cstdio>
 #include <fstream>
@@ -201,6 +202,23 @@ namespace file_util {
     struct stat buffer {};
     return stat(filename.c_str(), &buffer) == 0 && S_ISFIFO(buffer.st_mode);
   }
+
+  /**
+   * Get glob results using given pattern
+   */
+  vector<string> glob(const string& pattern) {
+    glob_t result;
+    vector<string> ret;
+
+    if (glob(pattern.c_str(), GLOB_TILDE, nullptr, &result) == 0) {
+      for (size_t i = 0_z; i < result.gl_pathc; ++i) {
+        ret.emplace_back(result.gl_pathv[i]);
+      }
+      globfree(&result);
+    }
+
+    return ret;
+  }
 }
 
 POLYBAR_NS_END