Glasgow | 26-SDC-JUL | Mirabelle Morah | Sprint 3 | Implement Shell Tools

implement-shell-tools/cat/cat.js

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+import { program } from "commander";
+import { promises as fs } from "node:fs";
+
+program
+  .name("cat")
+  .description("Concatenate and print files")
+  .argument("<paths...>", "The file paths to process")
+  .option("-n", "Number lines")
+  .option("-b", "Number non-blank lines");
+
+program.parse();
+
+function parseNumberMode(options) {
+  if (options.b) {
+    return "non-blank";
+  } else if (options.n) {
+    return "all";
+  } else {
+    return "none";
+  }
+}
+
+function calculatePrefix(
+  numberMode,
+  nonBlankLineNumber,
+  lineNumberIncludingBlanks,
+  thisLineIsBlank,
+) {
+  if (numberMode === "none") {
+    return "";
+  }
+  let lineNumber;
+  if (numberMode === "all") {
+    lineNumber = lineNumberIncludingBlanks;
+  } else {
+    if (thisLineIsBlank) {
+      return "";
+    } else {
+      lineNumber = nonBlankLineNumber;
+    }
+  }
+  return lineNumber.toString().padStart(6, " ") + "  ";
+}
+
+const numberMode = parseNumberMode(program.opts());
+
+for (const path of program.args) {
+  const content = await fs.readFile(path, "utf-8");
+  const lines = content.split("\n");
+  let nonBlankLineNumber = 1;
+  for (let i = 0; i < lines.length; i++) {
+    const line = lines[i];
+    if (i === lines.length - 1 && line === "") {
+      break;
+    }
+    const prefix = calculatePrefix(
+      numberMode,
+      nonBlankLineNumber,
+      i + 1,
+      line === "",
+    );
+    console.log(`${prefix}${line}`);
+    if (line !== "") {
+      nonBlankLineNumber += 1;
+    }
+  }
+}

implement-shell-tools/cat/package.json

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+{
+  "type": "module",
+  "dependencies": {
+    "commander": "^15.0.0"
+  }
+}

implement-shell-tools/ls/ls.js

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+import { promises as fs } from "node:fs";
+import process from "node:process";
+
+const argv = process.argv.slice(2);
+
+const flags = [];
+const paths = [];
+
+for (const arg of argv) {
+  if (arg.startsWith("-")) {
+    flags.push(arg);
+  } else {
+    paths.push(arg);
+  }
+}
+
+const showOnePerLine = flags.includes("-1");
+const showHiddenFiles = flags.includes("-a");
+
+let targets = paths;
+if (targets.length === 0) {
+  targets = ["."];
+}
+
+for (const target of targets) {
+  const info = await fs.stat(target);
+
+  let namesToShow;
+
+  if (info.isDirectory()) {
+    namesToShow = await fs.readdir(target);
+
+    if (showHiddenFiles) {
+      namesToShow = [".", "..", ...namesToShow];
+    } else {
+      namesToShow = namesToShow.filter((name) => !name.startsWith("."));
+    }
+
+    namesToShow.sort();
+  } else {
+    namesToShow = [target];
+  }
+
+  for (const name of namesToShow) {
+    console.log(name);
+  }
+}

implement-shell-tools/ls/package.json

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+{
+  "type": "module",
+  "dependencies": {
+    "commander": "^15.0.0"
+  }
+}

implement-shell-tools/wc/package.json

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+{
+  "type": "module",
+  "dependencies": {
+    "commander": "^15.0.0"
+  }
+}

implement-shell-tools/wc/wc.js

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+import { program } from "commander";
+import { promises as fs } from "node:fs";
+
+const argv = process.argv.slice(2);
+
+const flags = argv.filter((arg) => arg.startsWith("-"));
+const paths = argv.filter((arg) => !arg.startsWith("-"));
+
+const showLines = flags.includes("-l");
+const showWords = flags.includes("-w");
+const showBytes = flags.includes("-c");
+
+const noFlagsGiven = !showLines && !showWords && !showBytes;
+
+const columns = [];
+if (noFlagsGiven || showLines) columns.push("lines");
+if (noFlagsGiven || showWords) columns.push("words");
+if (noFlagsGiven || showBytes) columns.push("bytes");
+
+function countStats(content) {
+  const lines = (content.match(/\n/g) || []).length;
+  const words = content.split(/\s+/).filter((w) => w.length > 0).length;
+  const bytes = Buffer.byteLength(content, "utf-8");
+  return { lines, words, bytes };
+}
+
+// Read every file and collect its stats
+const rows = [];
+for (const path of paths) {
+  const content = await fs.readFile(path, "utf-8");
+  rows.push({ path, stats: countStats(content) });
+}
+
+// If there's more than one file, we also need a "total" row at the end
+if (rows.length > 1) {
+  const total = { lines: 0, words: 0, bytes: 0 };
+  for (const { stats } of rows) {
+    total.lines += stats.lines;
+    total.words += stats.words;
+    total.bytes += stats.bytes;
+  }
+  rows.push({ path: "total", stats: total });
+}
+
+const needsAlignment = columns.length > 1 || rows.length > 1;
+
+let width = 0;
+if (needsAlignment) {
+  for (const { stats } of rows) {
+    for (const col of columns) {
+      width = Math.max(width, String(stats[col]).length);
+    }
+  }
+
+  width = Math.max(width, 3);
+}
+
+for (const { path, stats } of rows) {
+  const parts = columns.map((col, index) => {
+    const text = String(stats[col]);
+    if (!needsAlignment) {
+      return text;
+    }
+    const padded = text.padStart(width, " ");
+
+    return index === 0 ? padded : " " + padded;
+  });
+
+  console.log(`${parts.join("")} ${path}`);
+}