add number only non-blank lines

Author: pathywang

implement-shell-tools/cat/cat.js

@@ -2,23 +2,32 @@ const fs = require("fs");
 
 const args = process.argv.slice(2);
 
-const numberLines = args[0] === "-n";
+const numberAll = args[0] === "-n";
+const numberNonBlank = args[0] === "-b";
 
-const files = numberLines ? args.slice(1) : args;
+const files = (numberAll || numberNonBlank)
+  ? args.slice(1)
+  : args;
 
 let lineNumber = 1;
 
 for (const file of files) {
   const content = fs.readFileSync(file, "utf8");
-
   const lines = content.split("\n");
 
   for (const line of lines) {
-    if (numberLines) {
+
+    if (numberAll) {
       console.log(`${String(lineNumber).padStart(6)}\t${line}`);
       lineNumber++;
+
+    } else if (numberNonBlank && line !== "") {
+      console.log(`${String(lineNumber).padStart(6)}\t${line}`);
+      lineNumber++;
+
     } else {
       console.log(line);
     }
+
   }
 }