implement cat

Author: PratiAmalden

implement-shell-tools/cat/cat.mjs

@@ -0,0 +1,45 @@
+import { program } from "commander";
+import {promises as fs} from "node:fs";
+
+program
+  .name("cat")
+  .description("read, display, and concatenate text files.")
+  .option("-n", " Number all output lines.")
+  .option("-b", " Number non-blank output lines.")
+  .arguments("<paths...>"); // allow more file paths
+
+program.parse();
+
+const options = program.opts();
+const paths = program.args;
+
+for(const path of paths){
+    let content;
+    try {
+        content = await fs.readFile(path, "utf-8")
+    } catch(err) {
+        console.error(`Error reading file "${path}": ${err.message} `);
+        continue;
+    }
+
+    // split file into lines
+    let lines = content.replace(/\n$/, "").split("\n");
+    
+    let lineNum = 1;
+
+    for (const line of lines){
+        if(options.b){
+            if(line.trim() !== ""){
+                console.log(`${lineNum.toString().padStart(5)}  ${line}`)
+                lineNum++;
+            } else {
+                console.log("");
+            }
+        } else if(options.n){
+            console.log(`${lineNum.toString().padStart(5)}  ${line}`)
+            lineNum++;
+        } else{
+            console.log(`${line}`)
+        }
+}
+}