如何在Node.js中通过child_process.spawn（）将长字符串传递给？

Question

I'm reading a pdf text from a s3 bucket using S3fs.readFile, and i would like to get the result, transform in string and immediately open a spawn child_process calling pdftotext, passing the string:

S3Fs.readFile('./my-pdf-in-s3-bucket', {encoding: 'binary'}, (error, result) => {
  mychild = child_process.spawn('pdftotext', [
    result.Body
  ]);
});

This is causing the spawn process break because the string is to long, and i don't want save the file in disk just to read it again.

Is it possible?

Thanks!

Answer 1

pdftotext should allow reading from stdin and writing to stdout (at least it worked for me with v0.41.0), so you could do this instead:

S3Fs.readFile('./my-pdf-in-s3-bucket', (err, result) => {
  if (err) throw err; // Handle better
  var cp = child_process.spawn('pdftotext', [ '-', '-' ]);
  cp.stdout.pipe(process.stdout);
  cp.on('close', (code, signal) => {
    console.log(`pdftotext finished with status ${code}`);
  });
  cp.stdin.end(result);
});

Or possibly better yet, you might be able to stream the file to the child process instead of buffering its entire contents in memory first:

var cp = child_process.spawn('pdftotext', [ '-', '-' ]);
var rs = S3Fs.createReadStream('./my-pdf-in-s3-bucket');
rs.on('error', (err) => {
  cp.kill();
});
cp.stdout.pipe(process.stdout);
cp.on('close', (code, signal) => {
  console.log(`pdftotext finished with status ${code}`);
});
rs.pipe(cp.stdin);