Birmingham | 2026-MAR-SDC | Joy Opachavalit | Sprint 3 | Implement shell tools

implement-shell-tools/cat/cat.js

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+#!/usr/bin/env node
+
+const fs = require('fs');
+const path = require('path');
+
+function cat(files, options) {
+  let lineNumber = 1;
+
+  files.forEach((file) => {
+    try {
+      const data = fs.readFileSync(file, 'utf8');
+      const lines = data.split('\n');
+
+      lines.forEach((line) => {
+        const prefix = options.numberNonEmpty && line.trim() ? `${lineNumber}\t` : options.numberLines ? `${lineNumber}\t` : '';
+        console.log(`${prefix}${line}`);
+        if (prefix) lineNumber++;
+      });
+    } catch (err) {
+      if (err.code === 'ENOENT') {
+        console.error(`cat: ${file}: No such file or directory`);
+      } else if (err.code === 'EACCES') {
+        console.error(`cat: ${file}: Permission denied`);
+      } else {
+        console.error(`cat: ${file}: An error occurred`);
+      }
+      process.exit(1);
+    }
+  });
+}
+
+function main() {
+  const args = process.argv.slice(2);
+  const options = {
+    numberLines: false,
+    numberNonEmpty: false,
+  };
+
+  const files = [];
+
+  args.forEach((arg) => {
+    if (arg === '-n') {
+      options.numberLines = true;
+    } else if (arg === '-b') {
+      options.numberNonEmpty = true;
+    } else {
+      files.push(arg);
+    }
+  });
+
+  if (files.length === 0) {
+    console.error('Usage: node cat.js [-n | -b] <file>...');
+    process.exit(1);
+  }
+
+  cat(files, options);
+}
+
+main();

implement-shell-tools/ls/ls.js

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+#!/usr/bin/env node
+
+const fs = require('fs');
+
+function listFiles(directory, options) {
+  try {
+    const files = fs.readdirSync(directory, { withFileTypes: true });
+
+    files.forEach((file) => {
+      if (!options.all && file.name.startsWith('.')) {
+        return; // Skip hidden files unless -a is specified
+      }
+      console.log(`${directory}/${file.name}`);
+    });
+  } catch (err) {
+    console.error(`ls: cannot access '${directory}': ${err.code === 'ENOENT' ? 'No such file or directory' : 'An error occurred'}`);
+    process.exit(1);
+  }
+}
+
+function main() {
+  const args = process.argv.slice(2);
+  const options = {
+    all: false,
+  };
+
+  const directories = [];
+
+  args.forEach((arg) => {
+    if (arg === '-1') {
+      // -1 is the default behavior, so no action needed
+    } else if (arg === '-a') {
+      options.all = true;
+    } else {
+      directories.push(arg);
+    }
+  });
+
+  if (directories.length === 0) {
+    directories.push('.');
+  }
+
+  directories.forEach((directory) => {
+    listFiles(directory, options);
+  });
+}
+
+main();

implement-shell-tools/wc/wc.js

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+#!/usr/bin/env node
+
+const fs = require('fs');
+
+function countFile(file, options) {
+  try {
+    const data = fs.readFileSync(file, 'utf8');
+
+    const lines = data.split('\n').length;
+    const words = data.split(/\s+/).filter(Boolean).length;
+    const bytes = Buffer.byteLength(data, 'utf8');
+
+    const results = [];
+    if (options.lines) results.push(lines);
+    if (options.words) results.push(words);
+    if (options.bytes) results.push(bytes);
+
+    console.log(`${results.join('\t')}\t${file}`);
+  } catch (err) {
+    console.error(`wc: ${file}: ${err.code === 'ENOENT' ? 'No such file or directory' : 'An error occurred'}`);
+    process.exit(1);
+  }
+}
+
+function main() {
+  const args = process.argv.slice(2);
+  const options = {
+    lines: false,
+    words: false,
+    bytes: false,
+  };
+
+  const files = [];
+
+  args.forEach((arg) => {
+    if (arg === '-l') {
+      options.lines = true;
+    } else if (arg === '-w') {
+      options.words = true;
+    } else if (arg === '-c') {
+      options.bytes = true;
+    } else {
+      files.push(arg);
+    }
+  });
+
+  if (files.length === 0) {
+    console.error('Usage: wc [-l | -w | -c] <file>...');
+    process.exit(1);
+  }
+
+  files.forEach((file) => {
+    countFile(file, options);
+  });
+}
+
+main();