Nodejs filesystem: Difference between revisions
From wikinotes
Line 22: | Line 22: | ||
See https://nodejs.org/api/fs.html | See https://nodejs.org/api/fs.html | ||
There are 2x separate APIs for interacting with files. | There are 2x separate APIs for interacting with files,<br> | ||
and several ''common object'' classes used in return values etc. | |||
<syntaxhighlight lang="javascript"> | <syntaxhighlight lang="javascript"> | ||
// APIs | |||
const fs = require('fs/promises'); // async/promise based | const fs = require('fs/promises'); // async/promise based | ||
const fs = require('fs'); // callback based | const fs = require('fs'); // callback based | ||
// Common Objects | |||
fs.Dir // a directory | |||
fs.Dirent // a file/directory inside a parent dir | |||
fs.Stats // size, filetype info, last modified, permissions | |||
fs.ReadStream / fs.WriteStream // stream io | |||
fs.FSWatcher / fs.StatWatcher // fs.watch()/fs.watchFile watch a file | |||
</syntaxhighlight> | </syntaxhighlight> | ||
Revision as of 20:24, 30 July 2021
filepaths
See https://nodejs.org/api/path.html
const path = require('path'); const filepath = path.resolve('foo.txt') // relative to abspath path.dirname(filepath) // '/home/you' path.basename(filepath) // 'foo.txt' path.extname(filepath) // '.txt' // nodejs does not expand ~ // so replace it with the envvar '~/.zshrc'.replace('~', process.env.HOME)
filesystem
Use the filesystem module to interact with files (read, write, size, ..).
See https://nodejs.org/api/fs.htmlThere are 2x separate APIs for interacting with files,
and several common object classes used in return values etc.// APIs const fs = require('fs/promises'); // async/promise based const fs = require('fs'); // callback based // Common Objects fs.Dir // a directory fs.Dirent // a file/directory inside a parent dir fs.Stats // size, filetype info, last modified, permissions fs.ReadStream / fs.WriteStream // stream io fs.FSWatcher / fs.StatWatcher // fs.watch()/fs.watchFile watch a filepromise api
const fs = require('fs/promises'); // async/await await fs.rename('/tmp/foo.txt', '/tmp/bar.txt'); // chained promises (? can I) fs.rename('/tmp/foo.txt', '/tmp/bar.txt') .then() .then()callback api
opening files
the file open modes are provided using the
flag
key in theoptions
hash./* a: append * w: write/replace * r: read * * appending '+' to any mode means read/write (ex: w+,r+,a+) */ const fs = require('fs'); fs.writeFileSync('/var/tmp/foo.txt', 'content', { flag: 'a' })const fs = require('fs'); const pfs = require('fs/promises'); const contents = 'abc\ndef'; // synchronous fs.writeFileSync('/var/tmp/foo.txt', contents) // async, callback based fs.writeFile('/var/tmp/foo.txt', contents, err => { if (err) { console.log(err); } }) // promise-based pfs.