node.js & fs & file read & file write

node.js & fs & file read & file write

https://nodejs.org/api/fs.html

const fs = require("fs");

// absolute path
fs.open("/open/some/file.txt", "r", (err, fd) => {
    if (err) {
        throw err;
    }
    fs.close(fd, (err) => {
        if (err) {
            throw err;
        }
    });
});

// relative path
fs.open("file.txt", "r", (err, fd) => {
    if (err) {
        throw err;
    }
    fs.close(fd, (err) => {
        if (err) {
            throw err;
        }
    });
});

readline

https://nodejs.org/api/readline.html

const readline = require('readline');

const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout
});

rl.question('What do you think of Node.js? ', (answer) => {
  // TODO: Log the answer in a database
  console.log(`Thank you for your valuable feedback: ${answer}`);

  rl.close();
});

const fs = require("fs");
const readline = require('readline');

const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout
});

// absolute path
// fs.open("/open/some/file.txt", "r", (err, fd) => {
//     if (err) {
//         throw err;
//     }
//     fs.close(fd, (err) => {
//         if (err) {
//             throw err;
//         }
//     });
// });

// relative path
fs.open("file.txt", "r", (err, fd) => {
    if (err) {
        throw err;
    }
    console.log(`fd =`, fd);// 3
    rl.on('line', (fd) => {
    console.log(`Received: ${fd}`);
    });
    fs.close(fd, (err) => {
        if (err) {
            throw err;
        }
    });
});

bug

https://stackoverflow.com/a/15554600/5934465

---

write & read

https://stackoverflow.com/a/15554600/5934465

https://stackoverflow.com/a/2497040/5934465

// preview.js

const fs = require("fs");
const readline = require("readline");

fs.writeFile("file.js", `export const APP_ENV = "preview";`, function(err) {
    if(err) {
        console.log(err);
        return err;
    }
    let env = "preview";
    console.log("The file was saved!", env);
});

let rd = readline.createInterface({
    input: fs.createReadStream("file.js"),
    output: process.stdout,
    console: false
});

rd.on("line", function(line) {
    console.log(`line =`, line);
});

// fs.writeFile("file.txt", "prview", function(err) {
//     if(err) {
//         console.log(err);
//         return err;
//     }
//     console.log("The file was saved!");
// });

// global.APP_ENV = "testing";
// let APP_ENV = global.APP_ENV;
// console.log(`APP_ENV =`, APP_ENV);

// let rd = readline.createInterface({
//     input: fs.createReadStream('file.txt'),
//     output: process.stdout,
//     console: false
// });

// rd.on('line', function(line) {
//     console.log(`line =`, line);
// });

// testing.js

const fs = require("fs");
const readline = require("readline");

fs.writeFile("file.js", `export const APP_ENV = "testing";`, function(err) {
    if(err) {
        console.log(err);
        return err;
    }
    let env = "testing";
    console.log("The file was saved!", env);
});

// const rl = readline.createInterface({
//     input: process.stdin,
//     output: process.stdout
// });

// absolute path
// fs.open("/open/some/file.txt", "r", (err, fd) => {
//     if (err) {
//         throw err;
//     }
//     fs.close(fd, (err) => {
//         if (err) {
//             throw err;
//         }
//     });
// });

// global.APP_ENV = "testing";
// let APP_ENV = global.APP_ENV;
// console.log(`APP_ENV =`, APP_ENV);

// relative path
// fs.open("file.js", "r", (err, fd) => {
//     if (err) {
//         throw err;
//     }
//     console.log(`fd =`, fd);// 3
//     fs.close(fd, (err) => {
//         if (err) {
//             throw err;
//         }
//     });
// });

let rd = readline.createInterface({
    input: fs.createReadStream("file.js"),
    output: process.stdout,
    console: false
});

rd.on("line", function(line) {
    console.log(`line =`, line);
});

// file.js

export const APP_ENV = "testing";

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global var

https://stackabuse.com/using-global-variables-in-node-js

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