Complete Module Tools: ls, cat, wc implementations

Complete Module Tools: ls, cat, wc implementations

Author: onurat

implement-shell-tools/cat/cat.js

@@ -0,0 +1,42 @@
+const fs = require("fs");
+
+const args = process.argv.slice(2);
+
+const showN = args.includes("-n");
+const showB = args.includes("-b");
+
+const files = args.filter(a => !a.startsWith("-"));
+
+let content = files.map(f => fs.readFileSync(f, "utf8")).join("");
+
+let lines = content.split("\n");
+
+// remove ONLY final empty line caused by trailing newline
+if (lines[lines.length - 1] === "") {
+  lines.pop();
+}
+
+let output = [];
+
+if (showN) {
+  let i = 1;
+  for (const line of lines) {
+    output.push(`${String(i).padStart(6)}  ${line}`);
+    i++;
+  }
+} else if (showB) {
+  let i = 1;
+  for (const line of lines) {
+    if (line !== "") {
+      output.push(`${String(i).padStart(6)}  ${line}`);
+      i++;
+    } else {
+      output.push("");
+    }
+  }
+} else {
+  output = lines;
+}
+
+// IMPORTANT: add final newline like real cat
+process.stdout.write(output.join("\n") + "\n");

implement-shell-tools/wc/wc.js

@@ -0,0 +1,58 @@
+const fs = require("fs");
+
+const args = process.argv.slice(2);
+
+const showLines = args.includes("-l");
+const showWords = args.includes("-w");
+const showBytes = args.includes("-c");
+
+const files = args.filter(a => !a.startsWith("-"));
+
+function getStats(text) {
+  return {
+    lines: text.split("\n").length - 1,
+    words: text.trim().split(/\s+/).filter(Boolean).length,
+    bytes: Buffer.byteLength(text)
+  };
+}
+
+function format(num) {
+  return String(num).padStart(8);
+}
+
+let totalLines = 0;
+let totalWords = 0;
+let totalBytes = 0;
+
+files.forEach(file => {
+  const content = fs.readFileSync(file, "utf8");
+  const stats = getStats(content);
+
+  totalLines += stats.lines;
+  totalWords += stats.words;
+  totalBytes += stats.bytes;
+
+  let output = [];
+
+  if (showLines) output.push(format(stats.lines));
+  else if (showWords) output.push(format(stats.words));
+  else if (showBytes) output.push(format(stats.bytes));
+  else output.push(format(stats.lines), format(stats.words), format(stats.bytes));
+
+  output.push(file);
+
+  console.log(output.join(" "));
+});
+
+if (files.length > 1) {
+  let output = [];
+
+  if (showLines) output.push(format(totalLines));
+  else if (showWords) output.push(format(totalWords));
+  else if (showBytes) output.push(format(totalBytes));
+  else output.push(format(totalLines), format(totalWords), format(totalBytes));
+
+  output.push("total");
+
+  console.log(output.join(" "));
+}