add simple ls tool (-1 and -a) in NodeJS

Author: Pezhman-Azizi

implement-shell-tools/ls/ls.js

@@ -0,0 +1,79 @@
+#!/usr/bin/env node
+
+const fs = require("fs");
+const path = require("path");
+
+// -------- args parsing --------
+const args = process.argv.slice(2);
+
+let onePerLine = false; // -1
+let showAll = false;    // -a
+let targets = [];
+
+for (const arg of args) {
+  if (arg === "-1") onePerLine = true;
+  else if (arg === "-a") showAll = true;
+  else targets.push(arg);
+}
+
+// Coursework only tests -1 variants, so enforce it clearly
+if (!onePerLine) {
+  console.error("Usage: node ls.js -1 [-a] [path]");
+  process.exit(1);
+}
+
+if (targets.length === 0) targets = ["."];
+if (targets.length > 1) {
+  console.error("ls.js: only one path is supported in this exercise");
+  process.exit(1);
+}
+
+const target = targets[0];
+
+// -------- helpers --------
+function sortLikeLs(names) {
+  return names.sort((a, b) => a.localeCompare(b));
+}
+
+function listDir(dirPath) {
+  let entries;
+  try {
+    entries = fs.readdirSync(dirPath, { withFileTypes: false });
+  } catch (err) {
+    console.error(`ls.js: cannot access '${dirPath}': ${err.message}`);
+    process.exit(1);
+  }
+
+  // readdirSync does NOT include "." and ".." — ls -a does.
+  if (showAll) {
+    // keep dotfiles + add . and ..
+    entries = [".", "..", ...entries];
+  } else {
+    // hide dotfiles
+    entries = entries.filter((name) => !name.startsWith("."));
+  }
+
+  entries = sortLikeLs(entries);
+
+  // -1 => one per line
+  for (const name of entries) {
+    process.stdout.write(name + "\n");
+  }
+}
+
+function listFile(filePath) {
+  // ls -1 file => prints the file name
+  process.stdout.write(path.basename(filePath) + "\n");
+}
+
+// -------- main --------
+let stat;
+try {
+  stat = fs.statSync(target);
+} catch (err) {
+  console.error(`ls.js: cannot access '${target}': ${err.message}`);
+  process.exit(1);
+}
+
+if (stat.isDirectory()) listDir(target);
+else listFile(target);