Redirecting stdout to file nodejs

Question

I\'ve created:

var access = fs.createWriteStream(\'/var/log/node/api.access.log\', { flags: \'w\' });

Then piped:

process.s         


        

Answer 1

Originally based on @Anatol-user3173842 answer

But in my case I needed to hook the stdout & stderr and also write into a file.

So for those who need to keep the normal stdout behaviour in addition to writing into the file. Use the following.

For non-errors:

// stdout logging hook
const stdoutWrite0 = process.stdout.write;
process.stdout.write = (args) => { // On stdout write
  CustomLogger.writeToLogFile('log', args); // Write to local log file
  args = Array.isArray(args) ? args : [args]; // Pass only as array to prevent internal TypeError for arguments
  return stdoutWrite0.apply(process.stdout, args);
};

For errors:

// stderr logging hook
const stderrWrite0 = process.stderr.write;
process.stderr.write = (args) => { // On stderr write
  CustomLogger.writeToLogFile('error', args); // Write to local error file
  args = Array.isArray(args) ? args : [args]; // Pass only as array to prevent internal TypeError for arguments
  return stderrWrite0.apply(process.stderr, args);
};

// uncaught exceptions
process.on('uncaughtException', (err) => {
  CustomLogger.writeToLogFile('error', ((err && err.stack) ? err.stack : err));
});

Here is the CustomLogger code, where I also separate the log files by date:

export class CustomLogger {

 static LOGS_DIR = 'location-of-my-log-files';

 private static logDailyName(prefix: string): string {
   const date = new Date().toLocaleDateString().replace(/\//g, '_');
   return `${CustomLogger.LOGS_DIR}/${prefix}_${date}.log`;
 }

 private static writeToLogFile(prefix, originalMsg) {
   const timestamp   = Date.now();
   const fileName    = this.logDailyName(prefix);
   const logMsg      = prepareForLogFile(originalMsg);
   fs.appendFileSync(fileName, `${timestamp}\t${logMsg}\n\n`);
   return originalMsg;
 }
}