Sugar to open and close a file descriptor
npm install fs-lotusSugar to open and close a file descriptor.
    
``js
const open = require('fs-lotus')
, fs = require('fs')
const readExactly = function (filename, pos, length, done) {
open(filename, 'r', function (err, fd, close) {
if (err) return done(err)
fs.read(fd, Buffer(length), 0, length, pos, function (err, bytesRead, buf) {
if (err) return close(done, err)
if (bytesRead !== length) {
return close(done, new Error('End of file'))
}
close(done, null, buf)
})
})
}
`
The open function has the same signature as [fs.open(path, flags[, mode], callback)](https://nodejs.org/api/fs.html#fs_fs_open_path_flags_mode_callback). Except that callback also receives a close(callback, err, ...args) function, which calls fs.close for you. An error from fs.close (if any) will be combined with your error (if any).
This pattern ensures that our readExactly function doesn't leak fd's.
`js
readExactly('readme.md', 0, 10, function (err, buf) {
console.log(buf.toString()) // '# fs-lotus'
})
readExactly('readme.md', 1e5, 10, function (err, buf) {
console.log(err.toString()) // 'Error: End of file'
})
`
With npm do:
`
npm install fs-lotus
MIT © Vincent Weevers