Implement cat, ls, and wc commands with line, word, and byte counting features

Author: mervereis

implement-shell-tools/cat/cat.js

@@ -0,0 +1,50 @@
+const fs = require("fs");
+
+const args = process.argv.slice(2);
+
+let numberLines = false;
+let numberNonBlank = false;
+const files = [];
+
+for (const arg of args) {
+  if (arg === "-n") {
+    numberLines = true;
+  } else if (arg === "-b") {
+    numberNonBlank = true;
+  } else {
+    files.push(arg);
+  }
+}
+
+if (numberNonBlank) {
+  numberLines = false;
+}
+
+let lineNumber = 1;
+
+for (const file of files) {
+  try {
+    const contents = fs.readFileSync(file, "utf8");
+    const lines = contents.split("\n");
+
+    lines.forEach((line, index) => {
+      const output = index < lines.length - 1 ? line + "\n" : line;
+
+      if (numberNonBlank) {
+        if (line.trim() === "") {
+          process.stdout.write(output);
+        } else {
+          process.stdout.write(`${String(lineNumber).padStart(6)}\t${output}`);
+          lineNumber++;
+        }
+      } else if (numberLines) {
+        process.stdout.write(`${String(lineNumber).padStart(6)}\t${output}`);
+        lineNumber++;
+      } else {
+        process.stdout.write(output);
+      }
+    });
+  } catch (err) {
+    console.error(`cat: ${file}: ${err.message}`);
+  }
+}

implement-shell-tools/ls/ls.js

@@ -0,0 +1,52 @@
+const fs = require("fs");
+
+const args = process.argv.slice(2);
+
+let onePerLine = false;
+let showHidden = false;
+let paths = [];
+
+for (let i = 0; i < args.length; i++) {
+  if (args[i] === "-1") {
+    onePerLine = true;
+  } else if (args[i] === "-a") {
+    showHidden = true;
+  } else {
+    paths.push(args[i]);
+  }
+}
+if (paths.length === 0) {
+  paths.push(".");
+}
+
+for (let i = 0; i < paths.length; i++) {
+  let path = paths[i];
+
+  try {
+    if (fs.statSync(path).isFile()) {
+      console.log(path);
+    } else {
+      let files = fs.readdirSync(path);
+
+      files.sort();
+
+      for (let j = 0; j < files.length; j++) {
+        let file = files[j];
+        if (!showHidden && file.startsWith(".")) {
+          continue;
+        }
+        if (onePerLine) {
+          console.log(file);
+        } else {
+          process.stdout.write(file + " ");
+        }
+      }
+
+      if (!onePerLine) {
+        console.log();
+      }
+    }
+  } catch (error) {
+    console.log("Cannot access: " + path);
+  }
+}

implement-shell-tools/wc/wc.js

@@ -0,0 +1,82 @@
+const fs = require("fs");
+
+const args = process.argv.slice(2);
+
+let countLines = false;
+let countWords = false;
+let countBytes = false;
+
+let files = [];
+
+for (let arg of args) {
+  if (arg === "-l") {
+    countLines = true;
+  } else if (arg === "-w") {
+    countWords = true;
+  } else if (arg === "-c") {
+    countBytes = true;
+  } else {
+    files.push(arg);
+  }
+}
+
+if (!countLines && !countWords && !countBytes) {
+  countLines = true;
+  countWords = true;
+  countBytes = true;
+}
+
+let totalLines = 0;
+let totalWords = 0;
+let totalBytes = 0;
+let filesCounted = 0;
+
+function countFile(fileName) {
+  try {
+    const content = fs.readFileSync(fileName, "utf8");
+    let lines = content.split("\n").length - 1;
+    let words = content
+      .trim()
+      .split(/\s+/)
+      .filter((word) => word.length > 0).length;
+    let bytes = Buffer.byteLength(content);
+    totalLines += lines;
+    totalWords += words;
+    totalBytes += bytes;
+    filesCounted++;
+    let result = "";
+    if (countLines) {
+      result += lines + " ";
+    }
+    if (countWords) {
+      result += words + " ";
+    }
+    if (countBytes) {
+      result += bytes + " ";
+    }
+    result += fileName;
+    console.log(result);
+  } catch (error) {
+    console.log("Cannot read file: " + fileName);
+  }
+}
+
+for (let file of files) {
+  countFile(file);
+}
+
+if (filesCounted > 1) {
+  let result = "";
+  if (countLines) {
+    result += totalLines + " ";
+  }
+  if (countWords) {
+    result += totalWords + " ";
+  }
+  if (countBytes) {
+    result += totalBytes + " ";
+  }
+  result += "total";
+
+  console.log(result);
+}