[JavaScript] Download base64 encoded file within a browser

            const sBase64 = "JVBERi0xLjQKJcOkw7zDtsOfCjIgMCBvYmoKPDwvTGVuZ3....."
            const arrayBuffer = new Uint8Array([...window.atob(sBase64)].map(char => char.charCodeAt(0)))
            const fileLink = document.createElement('a')

            fileLink.href = window.URL.createObjectURL(new Blob([arrayBuffer]))
            fileLink.setAttribute('download', "example.pdf")
            document.body.appendChild(fileLink)
            fileLink.click()

Or use the npm package FileSaver.

import { saveAs } from "file-saver";

const sBase64 = "JVBERi0xLjQKJcOkw7zDtsOfCjIgMCBvYmoKPDwvTGVuZ3....."
const buffer = Buffer.from(sBase64, "base64")
saveAs(new Blob([buffer]), "example.pdf")

[nodejs] read and write a file

https://nodejs.dev/learn/reading-files-with-nodejs

https://nodejs.dev/learn/writing-files-with-nodejs

        const fs = require("fs")

        try {
            // read from local folder
            const localPDF = fs.readFileSync('PDFs/myFile.pdf')

            //write back to local folder
            fs.writeFileSync('PDFs/writtenBack.pdf', localPDF )

        } catch (err) {
            console.error(err)
        }

Converting to Base64

        try {
            // read from local folder
            const localPDF = fs.readFileSync('PDFs/myFile.pdf')
            const localBase64 = localPDF.toString('base64')

            //write back to local folder
            fs.writeFileSync(`PDFs/writtenBack.pdf`, localBase64, {encoding: 'base64'})

        } catch (err) {
            console.error(err)
        }

Reading and writing using streams with pipe

        //read and write local file
        const reader = fs.createReadStream("PDFs/myFile.pdf")
        const writer = fs.createWriteStream('PDFs/writtenBack.pdf');
        reader.pipe(writer)

[Shell] User and Group management & File permissions

  • User and Group management
    • id
    • useradd
      • -c – Full name
      • -e – Expiration date
      • -s – Default shell
      • -d – Home directory
    • passwd
    • usermod
      • -l – rename
      • -L – Lock
      • -U – unlock
    • userdel
      • -r – remove user data
    • groupadd
    • groupmod
    • gpasswd [-a -d -A] [user1, user2] [group]
    • newgrp [group]
  • su vs. su – vs. sudo
    • visudo
  • File permissions
    • UGO – User, Group, Other
    • RWX – Read, Write, Execute
    • chmod -R g+x (grant recursive execute permission to group)
      • r = 4
      • w = 2
      • x = 1
      • = 0
      • rwxrwxrwx = 777
      • rw-rw-rw- = 666
      • rwxrwxr–- = 774
      • rw-rw—- = 660
      • rw-r—–- = 640
    • chown
    • chgrp
    • umask

https://www.sluug.org/resources/presentations/2020/2020-02-12_permissions.pdf