Implement 'wc' command to count lines, words, and bytes in files

Author: Geraldine-Edwards

implement-shell-tools/wc/wc.js

@@ -0,0 +1,85 @@
+import { program } from "commander";
+import { promises as fs } from "node:fs";
+import process from "node:process";
+
+// configure the CLI program with its name, description, arguments, options, and actions (the help instructions)
+program
+  .name("wc")
+  .description("An alternative to the 'wc' command")
+  .argument("<files...>", "The file(s) to count lines/words/bytes")
+  .option("-l", "Count lines")
+  .option("-w", "Count words")
+  .option("-c", "Count bytes")
+  .action(async (files, options) => {
+        try {
+            // call newWc for all files
+            await newWc(files, options)
+        } catch (err) {
+        console.error(`Error: ${err.message}`);
+        }
+  });
+
+  program.parse(process.argv);
+
+//helper function to format string for output
+function formatCount(count) {
+    return count.toString().padStart(3);
+}
+
+
+// helper function to print the wc outputs per case
+function printWcOutput(lineCount, wordCount, byteCount, file, options, noFlags) {
+    const parts = [];
+
+    if (noFlags || options.l) parts.push(formatCount(lineCount));
+    if (noFlags || options.w) parts.push(formatCount(wordCount));
+    if (noFlags || options.c) parts.push(formatCount(byteCount));
+
+    parts.push(file);
+    console.log(parts.join(" "));
+}
+
+async function newWc(files, options) {
+
+    const noFlags =
+    !options.l &&
+    !options.w &&
+    !options.c;
+
+    // set the counts variables
+    let totalLines = 0;
+    let totalWords = 0;
+    let totalBytes = 0;
+
+    for (const file of files) {
+
+        try {
+            // read each file into a single text string
+            const content = await fs.readFile(file, "utf8");
+
+            // count lines by splitting on '\n' and subtracting 1 because
+            // each newline creates an extra array element, so length-1 equals the number of newline characters
+            const lineCount = content.split("\n").length - 1;
+
+            // .filter(Boolean) ensures that falsy values like "" (empty string), null, undefined, 0, false are removed
+            const wordCount = content.split(/\s+/).filter(Boolean).length;
+        
+            // calculates the number of bytes the file uses when encoded as UTF-8.
+            // different than just counting chars as some chars (like emojis, accented letters, etc) take more than 1 byte
+            const byteCount = Buffer.byteLength(content, "utf8");
+
+            // update the count
+            totalLines += lineCount;
+            totalWords += wordCount;
+            totalBytes += byteCount;
+
+            printWcOutput(lineCount, wordCount, byteCount, file, options, noFlags);     
+        } catch (err) {
+            console.error(`Error reading file ${file}: ${err.message}`);
+        }
+    }
+    if (files.length > 1) {
+    // print the totals as wc does
+    printWcOutput(totalLines, totalWords, totalBytes,  "total", options, noFlags);
+}
+}