cat.js

import { program } from "commander";
import process from "node:process";
import { promises as fs } from "node:fs";

program
    .name("cat")
    .description("print the content of file")
    .option("-n, --line-numbers","Number the output lines, starting at 1")
    .option("-b, --number-nonblank", "Number non-empty output lines, overrides -n")
    .argument("<paths...>", "The file path(s) to process"); // to support multiple file
program.parse();

const argv = program.args;
const options = program.opts();
if (argv.length === 0) {
    console.error(`No file paths provided`);// to support more files 
    process.exit(1);
}

let lineCounter = 1;

for (const path of argv) {
    try {
const content = await fs.readFile(path, "utf-8");
const lines= content.split(/\r?\n/);
if (lines.length && lines[lines.length - 1] === '') {//// Remove trailing empty line if it's just from the final newline
    lines.pop();
}

if (options.numberNonblank) {
            lines.forEach((line) => {
                if (line.trim() === "") {
                    console.log(""); // Blank line, no number
                } else {
                    const lineNumber = String(lineCounter++).padStart(6, " ");
                    console.log(`${lineNumber}\t${line}`);
                }
            });
        
}else if (options.lineNumbers) {
    lines.forEach((line) => {
        const lineNumber = String(lineCounter++).padStart(6, ' ');
        console.log(`${lineNumber}\t${line}`)
    });
   
} else {
    process.stdout.write(content);
    if (!content.endsWith('\n')) process.stdout.write('\n');
        }
    } catch (err) {
        console.error(`cat: ${path}: ${err.message}`);
    }
}