WestMidlands | SDC-NOV-2025 | SARA TAHIR | Sprint 3 | Implement Shell Tools

implement-shell-tools/.gitignore

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+# Node modules
+node_modules/
+
+# Package lock file (optional)
+package-lock.json

implement-shell-tools/cat/file.js

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+//On macOS (BSD cat), the -n option resets numbering for each file, so multiple files start again at 1,
+//when you run cat -n sample-files/*.txt
+//This Node.js script mimics GNU cat, where -n continues numbering across all files instead of restarting.
+import { program } from "commander";
+import {promises as fs} from "node:fs"
+
+ //configuring the program here to run flags.
+
+program
+  .name("cat")
+  .description("Concatenate and print files")
+  .option("-n, --number", "Number all output lines")
+  .option("-b, --number-nonblank", "Number non-blank output lines") 
+  .argument("<files...>", "File paths to display")
+  .parse(process.argv);//Parse command line arguments (reads process.argv and interprets it)
+
+
+//Constants
+const paddingWidth = 6; // width for line number padding
+
+// Helper function to format a line with numbering
+function formatLine(line, lineNumber, numberAll, numberNonBlank) {
+  if (numberAll) {
+    return `${lineNumber.toString().padStart(paddingWidth)}  ${line}`;
+  }
+  if (numberNonBlank) {
+    if (line.trim() === "") {
+      return line; // blank line, no number
+    }
+    return `${lineNumber.toString().padStart(paddingWidth)}  ${line}`;
+  }
+  return line; // no numbering
+}
+const options = program.opts(); 
+const files = program.args; // Array of file paths passed as arguments
+
+let lineNumber = 1; // shared across all files
+
+for (const file of files) {
+  const content = await fs.readFile(file, "utf-8"); 
+  let lines = content.split("\n");
+  // Remove trailing empty line if file ends with newline
+  if (lines.length > 0 && lines[lines.length - 1] === "") {
+    lines.pop();
+  }
+
+  for (const line of lines) {
+    const formatted = formatLine(line, lineNumber, options.number, options.numberNonblank);
+    console.log(formatted);
+
+    // Increment line number if numbering applies
+    if (options.number || (options.numberNonblank && line.trim() !== "")) {
+      lineNumber++;
+    }
+  }
+}

implement-shell-tools/ls/ls.js

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+import { program } from "commander";
+import { promises as fs } from "node:fs";
+
+//configuring 
+program
+  .name("ls")
+  .description("list directory contents")
+  .option("-1, --one", "Outputs are printed one entry per line")
+  .option("-a, --all","Show all files including hidden files that start with a .")
+  .argument("[directory]", "Directory to list", "."); // "." means current directory
+
+//interpret the program
+program.parse();
+const options = program.opts();
+const directory = program.args[0] || "."; //get dir arg- 1st arg in program.args array || if no arg default to current dir
+
+
+let files = await fs.readdir(directory); //read the dir to get array of filenames
+
+//Handle -a (include hidden files)
+// Node's fs.readdir() does not include the special directory entries "." (current dir)
+// and ".." (parent dir). The real `ls -a` command shows them, so we add them manually here
+// to match the behavior of `ls -a`.
+if (options.all) { 
+
+  files.unshift(".."); 
+  files.unshift(".");
+} else {
+  files = files.filter(name => !name.startsWith("."));
+}
+
+if (options.one) { // Print each file on its own line
+  for (const file of files) {
+    console.log(file);
+  }
+}
+else {
+  console.log(files.join(" "));// Default: join with spaces (like ls without -1)
+}

implement-shell-tools/package.json

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+{
+    "type": "module",
+    "dependencies": {
+        "commander": "^14.0.2"
+    }
+}

implement-shell-tools/wc/wc.js

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+import { program } from "commander";
+import { promises as fs } from "node:fs";
+
+//configuring 
+program
+  .name("wc")
+  .description("Print newline, word, and byte counts for each file")
+  .option("-l, --lines", "Print the newline counts")
+  .option("-w, --words", "Print the word counts")
+  .option("-c, --bytes", "Print the byte counts")
+  .argument("<files...>", "File paths to process")
+//Interpret the program
+  program.parse()
+const options = program.opts()
+const files = program.args //Interpreting parsed data
+
+
+//helper function to calculate all counts 
+async function getCounts(file){
+  const content = await fs.readFile(file, "utf-8");
+  const lineCount = content.split("\n").length -1;//split("\n") returns one more element than the actual number so length-1,
+  const wordCount = content.trim().split(/\s+/).length;
+  const byteCount = Buffer.byteLength(content, "utf-8"); //Calculate how many bytes the string uses in UTF-8 (important because some characters use more than 1 byte)
+  return { lineCount, wordCount, byteCount };
+}
+//initiating totals
+let totalLines = 0;
+let totalWords = 0;
+let totalBytes = 0;
+
+for (const file of files) {
+  const { lineCount, wordCount, byteCount } = await getCounts(file);
+
+  totalLines += lineCount;
+  totalWords += wordCount;
+  totalBytes += byteCount;
+
+let output = "";
+  if (options.lines) output += `${lineCount} `;
+  if (options.words) output += `${wordCount} `;
+  if (options.bytes) output += `${byteCount} `;
+  if (!options.lines && !options.words && !options.bytes) {
+    output += `${lineCount} ${wordCount} ${byteCount} `;
+  }
+  output += file;
+  console.log(output);
+}
+
+
+  //Print totals if multiple files
+if (files.length > 1) {
+  let totalOutput = "";
+  if (options.lines) totalOutput += `${totalLines} `;
+  if (options.words) totalOutput += `${totalWords} `;
+  if (options.bytes) totalOutput += `${totalBytes} `;
+  if (!options.lines && !options.words && !options.bytes) {
+    totalOutput += `${totalLines} ${totalWords} ${totalBytes} `;
+  }
+  totalOutput += "total";
+  console.log(totalOutput);
+}