London| 2026-MAR-SDC | Imran Mohamed | Sprint 3 | Implement shell tools

implement-shell-tools/cat/cat.mjs

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+import {program} from 'commander';
+import {promises as fs} from 'node:fs';
+import process from 'node:process';
+
+program
+    .name('cat')
+    .description('Concatenates and prints the contents of files.')
+    .argument('<paths...>', 'The paths to the files to concatenate')
+    .option('-n, --number', 'Number all output lines')
+    .option('-b, --number-nonblank', 'Number nonempty output lines');
+
+program.parse();
+
+const argv = program.args;
+const options = program.opts();
+
+if (argv.length < 1) {
+	console.error(
+		`Expected at least 1 argument (a path) to be passed but got ${argv.length}.`,
+	);
+	process.exit(1);
+}
+
+let showLineNumbers = options.number || false;
+let showNonEmptyLineNumbers = options.numberNonblank || false;
+
+if (showLineNumbers && showNonEmptyLineNumbers) {
+    showLineNumbers = false;
+}
+
+let lineNumber = 1;
+const spacer = '    ';
+
+for (const path of argv) {
+    const content = await fs.readFile(path, 'utf-8');
+    const lines = content.split('\n');
+    while (lines.length > 0 && lines[lines.length - 1] === '') {
+        lines.pop();
+    }
+    for (const line of lines) {
+        if (showLineNumbers) {
+            process.stdout.write(`${spacer} ${lineNumber++}  ${line}\n`);
+        } else if (showNonEmptyLineNumbers && line.trim() !== '') {
+            process.stdout.write(`${spacer} ${lineNumber++}  ${line}\n`);
+        } else {
+            process.stdout.write(`${line}\n`);
+        }
+    }
+}

implement-shell-tools/cat/package.json

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+{
+  "name": "cat",
+  "version": "1.0.0",
+  "description": "You should already be familiar with the `cat` command line tool.",
+  "main": "index.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "keywords": [],
+  "author": "",
+  "license": "ISC",
+  "dependencies": {
+    "commander": "^14.0.3"
+  }
+}

implement-shell-tools/ls/ls.mjs

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+import { program } from 'commander';
+import process from 'node:process';
+import { promises as fs } from 'node:fs';
+
+program
+    .name('ls')
+    .description('Lists the contents of a directory.')
+    .argument('[path]', 'The path to the directory to list, defaults to the current directory')
+    .option('-a, --all', 'Do not ignore entries starting with .')
+    .option('-1', 'List one file per line');
+
+program.parse();
+
+const argv = program.args;
+const path = argv[0] || '.';
+
+let showAll = program.opts().all || false;
+let onePerLine = program.opts()['1'] || false;
+
+try {
+    const files = await fs.readdir(path);
+    files.sort((a, b) => a.localeCompare(b, undefined, { numeric: true, sensitivity: 'base' }));
+    for (const file of files) {
+        if (showAll || !file.startsWith('.')) {
+            if (onePerLine) {
+                process.stdout.write(`${file}\n`);
+            } else {
+                process.stdout.write(`${file} `);
+            }
+        }
+    }
+} catch (err) {
+    process.stderr.write(`cannot access '${path}': No such file or directory\n`);
+    process.exit(1);
+}

implement-shell-tools/ls/package.json

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+{
+  "name": "ls",
+  "version": "1.0.0",
+  "description": "You should already be familiar with the `ls` command line tool.",
+  "main": "index.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "keywords": [],
+  "author": "",
+  "license": "ISC",
+  "dependencies": {
+    "commander": "^14.0.3"
+  }
+}

implement-shell-tools/wc/package.json

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+{
+  "name": "wc",
+  "version": "1.0.0",
+  "description": "You should already be familiar with the `wc` command line tool.",
+  "main": "wc.mjs",
+  "type": "module",
+  "dependencies": {
+    "commander": "^14.0.3"
+  },
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "keywords": [],
+  "author": "",
+  "license": "ISC"
+}

implement-shell-tools/wc/wc.mjs

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+import { program } from 'commander';
+import process from 'node:process';
+import { promises as fs } from 'node:fs';
+
+program
+    .name('wc')
+    .description('Counts the number of lines, words, and characters in a file.')
+    .argument('<path>', 'The path to the file to analyze')
+    .option('-l, --lines', 'Only count lines')
+    .option('-w, --words', 'Only count words')
+    .option('-c, --characters', 'Only count characters');
+
+program.parse();
+
+const argv = program.args;
+
+if (argv.length != 1) {
+    console.error(
+        `Expected exactly 1 argument (a path) to be passed but got ${argv.length}.`);
+    process.exit(1);
+}
+const path = argv[0];
+const options = program.opts();
+
+let showLines = options.lines || (!options.words && !options.characters);
+let showWords = options.words || (!options.lines && !options.characters);
+let showCharacters = options.characters || (!options.lines && !options.words);
+
+const content = await fs.readFile(path, 'utf-8');
+
+const lineCount = content.split('\n').filter(Boolean).length;
+const wordCount = content.split(' ').filter(Boolean).length;
+const characterCount = content.length;
+console.log(` ${showLines ? lineCount : ''}  ${showWords ? wordCount : ''} ${showCharacters ? characterCount : ''} ${path}`);