Add tee file for logging

Author: dallison

toolbelt/logging.cc

@@ -1,4 +1,4 @@
-// Copyright 2023 David Allison
+// Copyright 2023,2025 David Allison
 // All Rights Reserved
 // See LICENSE file for licensing information.
 
@@ -132,11 +132,26 @@ void Logger::Log(LogLevel level, const char *fmt, ...) {
   va_end(ap);
 }
 
+absl::Status Logger::SetTeeFile(const std::string &filename, bool truncate) {
+  if (tee_stream_ != nullptr) {
+    fclose(tee_stream_);
+  }
+  tee_stream_ = fopen(filename.c_str(), truncate ? "w" : "a");
+  if (tee_stream_ == nullptr) {
+    return absl::InternalError(absl::StrFormat("Failed to open tee file %s: %s",
+                                               filename, strerror(errno)));
+  }
+  return absl::OkStatus();
+}
+
 void Logger::VLog(LogLevel level, const char *fmt, va_list ap) {
   if (level < min_level_) {
     return;
   }
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wformat-nonliteral"
   size_t n = vsnprintf(buffer_, sizeof(buffer_), fmt, ap);
+#pragma clang diagnostic pop
 
   // Strip final \n if present.  Refactoring from printf can leave
   // this in place.
@@ -196,6 +211,11 @@ void Logger::Log(LogLevel level, uint64_t timestamp, const std::string &source,
     break;
   }
 
+  if (tee_stream_ != nullptr) {
+    fprintf(tee_stream_, "%s %s: %s: %s: %s\n", timebuf, subsystem_.c_str(),
+            LogLevelAsString(level), source.c_str(), text.c_str());
+    fflush(tee_stream_);
+  }
   if (level == LogLevel::kFatal) {
     abort();
   }
@@ -311,7 +331,9 @@ void Logger::LogColumnar(const char *timebuf, LogLevel level,
     // clang-format off.
     fprintf(output_stream_, "%-*s%s%-*s%s\n", prefix_length,
             first_line ? prefix.c_str() : "",
-            color::SetColor(ColorForLogLevel(level)).c_str(), int(column_widths_[4]), segment.c_str(), color::ResetColor().c_str());
+            color::SetColor(ColorForLogLevel(level)).c_str(),
+            int(column_widths_[4]), segment.c_str(),
+            color::ResetColor().c_str());
     // clang-format on
     start += segment.size();
     if (start >= text.size()) {

toolbelt/logging.h

@@ -1,10 +1,11 @@
-// Copyright 2023 David Allison
+// Copyright 2023,2025 David Allison
 // All Rights Reserved
 // See LICENSE file for licensing information.
 
 #ifndef __TOOLBELT_LOGGING_H
 #define __TOOLBELT_LOGGING_H
 
+#include "absl/status/status.h"
 #include "toolbelt/color.h"
 #include <stdarg.h>
 #include <string>
@@ -59,6 +60,16 @@ class Logger {
   void Enable() { enabled_ = true; }
   void Disable() { enabled_ = false; }
 
+  // We can also tee the output to a file or a stream.  Calling this more than
+  // once will close the current stream and open a new one.
+  absl::Status SetTeeFile(const std::string& filename, bool truncate = true);
+  void SetTeeStream(FILE *stream) {
+    if (tee_stream_ != nullptr) {
+      fclose(tee_stream_);
+    }
+    tee_stream_ = stream;
+  }
+
   // Log a message at the given log level.  If standard error is a TTY
   // it will be in color.
   virtual void Log(LogLevel level, const char *fmt, ...);
@@ -125,6 +136,7 @@ class Logger {
   int screen_width_;
   LogTheme theme_ = LogTheme::kDefault;
 
+  FILE* tee_stream_ = nullptr;
   static constexpr int kNumColumns = 5;
   size_t column_widths_[kNumColumns];
   color::Color colors_[kNumColumns];

toolbelt/sockets.cc

@@ -262,7 +262,6 @@ absl::StatusOr<ssize_t> Socket::SendMessage(char *buffer, size_t length,
   // the address passed as the buffer.
   int32_t *lengthptr = reinterpret_cast<int32_t *>(buffer) - 1;
   *lengthptr = htonl(length);
-
   ssize_t n = SendFully(c, fd_.Fd(), reinterpret_cast<char *>(lengthptr),
                         length + sizeof(int32_t), IsBlocking());
   if (n == -1) {