cat implementation with flags

Author: Priscilla-EM

implement-shell-tools/cat/mycat.js

@@ -5,18 +5,44 @@ import process from "node:process";
 program
   .name("mycat")
   .description("Outputs the content of the given file(s), like the cat command")
-  .argument("<path>", "The file path to read");
+  .option("-n", "Number all lines")
+  .option("-b", "Number non-blank lines only")
+  .argument("<files...>", "File paths to display");
 
 program.parse();
 
-const argv = program.args;
-if (argv.length !== 1) {
-  console.error(
-    `Expected exactly 1 argument (a path) to be passed but got ${argv.length}.`
-  );
-  process.exit(1);
-}
+const options = program.opts();
+const filePaths = program.args;
+
+let lineNumber = 1;
+
+for (const path of filePaths) {
+  try {
+    const content = await fs.readFile(path, "utf-8");
+    const lines = content.trimEnd().split("\n");
 
-const path = argv[0];
-const content = await fs.readFile(path, "utf-8");
-process.stdout.write(content);
+    for (const line of lines) {
+      const isBlank = line.trim() === "";
+
+      if (options.b) {
+        // -b: number only non-blank lines
+        if (!isBlank) {
+          process.stdout.write(`${String(lineNumber).padStart(6)}  ${line}\n`);
+          lineNumber++;
+        } else {
+          process.stdout.write("\n");
+        }
+      } else if (options.n) {
+        // -n: number all lines
+        process.stdout.write(`${String(lineNumber).padStart(6)}  ${line}\n`);
+        lineNumber++;
+      } else {
+        // no flags
+        process.stdout.write(line + "\n");
+      }
+    }
+  } catch (error) {
+    process.stderr.write(`Error reading file ${path}: ${error.message}\n`);
+    process.exit(1);
+  }
+}