London | 25-SDC-Nov | Jesus del Moral | Sprint 3| Implement Shell Tools

implement-shell-tools/cat/script-cat.js

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+#!/usr/bin/env node
+import { program } from "commander";
+import { promises as fs } from "node:fs";
+
+// Setup CLI
+program
+  .name("cat")
+  .description("Concatenate files and print on the standard output")
+  .option("-n, --number", "number all output lines")
+  .option("-b, --number-nonblank", "number nonempty output lines")
+  .argument("<path...>", "file(s) to read");
+
+program.parse();
+
+const files = program.args;
+const { number, numberNonblank } = program.opts();
+
+// Validate input
+if (files.length === 0) {
+  console.error("cat: missing file operand");
+  process.exit(1);
+}
+
+let lineNumber = 1;
+
+// Helper to print lines with optional numbering
+function printLine(line, shouldNumber) {
+  if (shouldNumber) {
+    console.log(`${String(lineNumber).padStart(6)}\t${line}`);
+    lineNumber++;
+  } else {
+    console.log(line);
+  }
+}
+
+for (const file of files) {
+  let content;
+  try {
+    content = await fs.readFile(file, "utf8");
+  } catch (err) {
+    console.error(`cat: ${file}: ${err.message}`);
+    continue;
+  }
+
+  const lines = content.split("\n");
+
+  for (let i = 0; i < lines.length; i++) {
+    const line = lines[i];
+
+    // Avoid printing an extra line if file ends with \n
+    if (i === lines.length - 1 && line === "") {
+      break;
+    }
+
+    const isBlank = line.trim() === "";
+
+    if (numberNonblank) {
+      printLine(line, !isBlank);
+    } else if (number) {
+      printLine(line, true);
+    } else {
+      printLine(line, false);
+    }
+  }
+}

implement-shell-tools/ls/script-ls.js

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+#!/usr/bin/env node
+import { program } from "commander";
+import fs from "fs";
+import path from "path";
+
+// Define CLI
+program
+  .name("ls-clone")
+  .description("A simple implementation of ls")
+  .option("-1", "list one file per line")
+  .option("-a", "include hidden files")
+  .argument("[dirs...]", "directories to list", "."); // default is current dir
+
+program.parse();
+
+const options = program.opts();
+const dirs = program.args.length ? program.args : ["."];
+const onePerLine = options["1"];
+const showAll = options.a;
+
+for (const dir of dirs) {
+  let files;
+  try {
+    files = fs.readdirSync(dir);
+  } catch (err) {
+    console.error(`ls-clone: cannot access '${dir}': No such file or directory`);
+    continue;
+  }
+
+  if (!showAll) {
+    files = files.filter(name => !name.startsWith("."));
+  }
+
+  // Output
+  if (onePerLine) {
+    files.forEach(f => console.log(f));
+  } else {
+    console.log(files.join("  "));
+  }
+}

implement-shell-tools/wc/script-wc.js

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+#!/usr/bin/env node
+import { program } from "commander";
+import { promises as fs } from "node:fs";
+import process from "node:process";
+
+// Setup CLI
+program
+  .name("wc-clone")
+  .description("A simplified implementation of the wc command")
+  .option("-l", "count lines")
+  .option("-w", "count words")
+  .option("-c", "count bytes")
+  .argument("[files...]", "files to process");
+
+program.parse();
+
+const options = program.opts();
+const files = program.args;
+
+if (files.length === 0) {
+  console.error("Please provide at least one file.");
+  process.exit(1);
+}
+
+// Count lines, words, bytes
+function countContent(content) {
+  const lines = content.split("\n").length;
+  const words = content.trim().split(/\s+/).filter(Boolean).length;
+  const bytes = Buffer.byteLength(content, "utf-8");
+  return { lines, words, bytes };
+}
+
+// Format output consistently
+function formatOutput(counts, label = "") {
+  const showAll = !options.l && !options.w && !options.c;
+  const parts = [];
+
+  if (options.l || showAll) parts.push(counts.lines.toString().padStart(8));
+  if (options.w || showAll) parts.push(counts.words.toString().padStart(8));
+  if (options.c || showAll) parts.push(counts.bytes.toString().padStart(8));
+
+  if (label) parts.push(label);
+
+  return parts.join(" ");
+}
+
+(async () => {
+  let total = { lines: 0, words: 0, bytes: 0 };
+  const multipleFiles = files.length > 1;
+
+  for (const file of files) {
+    let content;
+    try {
+      content = await fs.readFile(file, "utf-8");
+    } catch {
+      console.error(`wc-clone: cannot open '${file}': No such file`);
+      continue;
+    }
+
+    const counts = countContent(content);
+
+    total.lines += counts.lines;
+    total.words += counts.words;
+    total.bytes += counts.bytes;
+
+    console.log(formatOutput(counts, file));
+  }
+
+  if (multipleFiles) {
+    console.log(formatOutput(total, "total"));
+  }
+})();