async function run(ctx, argv) {
  let width = 80
  const paths = []
  for (let i = 1; i < argv.length; i++) {
    const a = argv[i]
    if (a === '-h' || a === '--help') {
      ctx.console.log('usage: fold [-w WIDTH] [FILE]...\nWrap each input line to WIDTH columns.')
      return
    }
    if ((a === '-w' || a === '--width') && argv[i + 1]) {
      width = parseInt(argv[++i], 10)
      if (!Number.isFinite(width) || width < 1) width = 80
      continue
    }
    if (a.startsWith('-') && a !== '-') {
      ctx.console.error('fold: unsupported option ' + a)
      ctx.exitCode = 1
      return
    }
    paths.push(a)
  }
  const b4 = ctx.b4a
  function wrapLine(line) {
    if (line.length <= width) return [line]
    const rows = []
    let rest = line
    while (rest.length > width) {
      rows.push(rest.slice(0, width))
      rest = rest.slice(width)
    }
    if (rest.length) rows.push(rest)
    return rows
  }
  function proc(text) {
    const lines = text.split('\n')
    for (let li = 0; li < lines.length; li++) {
      const isLast = li === lines.length - 1
      const line = lines[li]
      if (isLast && line === '' && lines.length > 1) continue
      for (const row of wrapLine(line)) ctx.console.log(row)
    }
  }
  if (!paths.length) {
    proc(bareStdin(ctx))
    return
  }
  for (const p of paths) {
    if (p === '-') {
      proc(bareStdin(ctx))
      continue
    }
    const b = await ctx.vfs.readFile(p)
    if (!b) {
      ctx.console.error('fold: ' + p + ': No such file')
      ctx.exitCode = 1
      continue
    }
    proc(b4.toString(b))
  }
}