Run shell from javascript. Want to call a bash script with many varied args? Put arg sets into JSON, `require('./my.json')`, form the command string and run it. Used with https://gist.github.com/LouisRitchie/9a90badb920bea29c65100a757b1c95d to get chapters from a book.

run_shell_from_javascript.js

const { exec } = require('child_process')
const fs = require('fs')

const SCRIPT_FILENAME = 'split_chapter_into_filename.sh'

function executeChildProcess(command, shouldLog) {
  const dir = exec(command, (err, stdout, stderr) => {
    if (shouldLog) {
      console.log(stdout)
    }
  })

  if (shouldLog) {
    dir.on('exit', code => {
      console.log(`exit code: ${code}`)
    })
  }
}

if (!fs.existsSync(SCRIPT_FILENAME)) {
  throw `${SCRIPT_FILENAME} does not exist; exiting.`
}

require('./pages.json').map((tuple, i) => executeChildProcess(`./${SCRIPT_FILENAME} textbook.djvu ${tuple[0] + 21} ${tuple[1] + 21} chapter_${i}.djvu`))