Prepend a string to beginning of each line of stdout/stderr.
npm install prepend-transform``bash`
npm install -S prepend-transform
`javascript
import pt from 'prepend-transform';
import * as cp from 'child_process';
const n = cp.spawn('bash');
n.stdout.pipe(pt('child stdout: ')).pipe(process.stdout);
n.stderr.pipe(pt('child stderr: ')).pipe(process.stderr);
``