implement cat with -n and -b flags

Author: Konvaly

implement-shell-tools/cat/cat.js

@@ -0,0 +1,54 @@
+import { promises as fs } from "node:fs";
+import process from "node:process";
+
+const args = process.argv.slice(2);
+
+if (args.length === 0) {
+  console.error("Usage: node cat.js [-n] [-b] <file...>");
+  process.exit(1);
+}
+const showAllLineNumbers = args.includes("-n");
+const showNonBlankNumbers = args.includes("-b");
+
+const filePaths = args.filter((arg) => !arg.startsWith("-"));
+
+let lineNumber = 1;
+
+for (const filePath of filePaths) {
+  const content = await fs.readFile(filePath, "utf-8");
+
+  if (!showAllLineNumbers && !showNonBlankNumbers) {
+    process.stdout.write(content);
+  } else {
+    const lines = content.split("\n");
+
+    for (let i = 0; i < lines.length; i++) {
+      const line = lines[i];
+
+      let isLastLine;
+      if (i === lines.length - 1) {
+        isLastLine = true;
+      } else {
+        isLastLine = false;
+      }
+
+      if (isLastLine && line === "") {
+        break;
+      }
+
+      if (showAllLineNumbers) {
+        const paddedNumber = String(lineNumber).padStart(6, " ");
+        process.stdout.write(`${paddedNumber}\t${line}\n`);
+        lineNumber++;
+      } else if (showNonBlankNumbers) {
+        if (line.trim() === "") {
+          process.stdout.write("\n");
+        } else {
+          const paddedNumber = String(lineNumber).padStart(6, " ");
+          process.stdout.write(`${paddedNumber}\t${line}\n`);
+          lineNumber++;
+        }
+      }
+    }
+  }
+}

implement-shell-tools/cat/package.json

@@ -0,0 +1,3 @@
+{
+  "type": "module"
+}