How Can I Execute Command Line Binaries Using Node.js?

Execute Command Line Binaries with Node.js

In Ruby, you can execute third-party binaries using the system method. In Node.js, there are two options for executing command line binaries: child_process.exec and child_process.spawn.

Buffered Output with child_process.exec

Use child_process.exec if you want to receive the entire output of the command at once.

const { exec } = require('child_process');
exec('cat *.js bad_file | wc -l', (err, stdout, stderr) => {
  if (err) {
    // Handle error
  } else {
    console.log(`stdout: ${stdout}`);
    console.log(`stderr: ${stderr}`);
  }
});

Streamed Output with child_process.spawn

Use child_process.spawn if you prefer to receive the output gradually in chunks as a stream.

const { spawn } = require('child_process');
const child = spawn('ls', ['-lh', '/usr']);

child.stdout.on('data', (chunk) => {
  // Data from standard output is here as buffers
});

child.on('close', (code) => {
  console.log(`child process exited with code ${code}`);
});

Synchronous Execution

For synchronous execution (not recommended for large output), use the child_process.execSync and child_process.spawnSync methods.

Note: For Node.js versions before ES5, refer to the following code for handling command line execution:

Buffered Output with child_process.exec

var exec = require('child_process').exec;
var cmd = 'prince -v builds/pdf/book.html -o builds/pdf/book.pdf';

exec(cmd, function(error, stdout, stderr) {
  // command output is in stdout
});

Streamed Output with child_process.spawn

var spawn = require('child_process').spawn;
var child = spawn('prince', [
  '-v', 'builds/pdf/book.html',
  '-o', 'builds/pdf/book.pdf'
]);

child.stdout.on('data', function(chunk) {
  // output will be here in chunks
});

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