implements-shell-tool

implement-shell-tools/cat/cat.js

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+#!/usr/bin/env node
+const fs = require('fs');
+const path = require('path');
+
+//shared line counter across all files(matches cat -n)
+let globalLineCounter = 1;
+
+function printFile(filePath, options) {
+    try {
+        const content = fs.readFileSync(filePath, 'utf-8');
+        const lines = content.split('\n');
+
+        lines.forEach((line) => {
+            if(options.numberNonEmpty) {
+                //-b option: number non-empty lines
+                if(line.trim()) {
+                    process.stdout.write(
+                        `${String(globalLineCounter).padStart(6)}\t${line}\n`
+                    );
+                    globalLineCounter++;
+                } else {
+                    process.stdout.write('\n');
+                }
+            } else if(options.numberAll) {
+                //-n option: number all lines
+                process.stdout.write(
+                    `${String(globalLineCounter).padStart(6)}\t${line}\n`
+                );
+                globalLineCounter++;
+            } else {
+                //default: just print the line
+                process.stdout.write(line + '\n');
+            }
+    });
+
+    } catch (error) {
+        console.error(`Error reading file ${filePath}: ${error.message}`);
+    }
+}
+
+function main() {
+    const args = process.argv.slice(2);
+    const options = {
+        numberNonEmpty: false,
+        numberAll: false,
+    };
+    const filePatterns = [];
+
+    args.forEach((arg) => {
+        if(arg === '-n') {
+            options.numberAll = true;
+        } else if(arg === '-b') {
+            options.numberNonEmpty = true;
+        } else {
+            filePatterns.push(arg);
+        }
+    });
+    // -b takes precedence over -n
+    if(options.numberNonEmpty) {
+        options.numberAll = false;
+    }
+
+    if(filePatterns.length === 0) {
+        console.log("cat: missing file operand");
+        process.exit(1);
+    }
+
+    const files = filePatterns;
+
+    files.forEach((file) => {
+        const resolvedPath = path.resolve(process.cwd(), file);
+        printFile(resolvedPath, options);
+    });
+    }
+
+main();

implement-shell-tools/ls/ls.js

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+#!/usr/bin/env node
+const fs = require('node:fs');
+const path = require('node:path');
+
+function listDirectory(dirPath, showAll, onePerLine) {
+    try {
+        const entries = fs.readdirSync(dirPath, { withFileTypes: true });
+        const filtered = entries.filter((entry) => showAll || !entry.name.startsWith('.'));
+
+        if(onePerLine) {
+            filtered.forEach(entry => console.log(entry.name));
+        } else {
+            const names = filtered.map(entry => entry.name);
+            console.log(names.join('  '));
+        }
+        } catch (error) {
+        console.error(`Error reading directory ${dirPath}: ${error.message}`);
+    }
+}
+function main() {
+    const args = process.argv.slice(2);
+    // Check for options
+    const showAll = args.includes('-a');
+    const onePerLine = args.includes('-1');
+    //remove options from args 
+    const directories = args.filter(arg => arg !== '-a' && arg !== '-1');
+
+    // If no directory is specified, list the current directory
+    if(directories.length === 0) {
+        listDirectory(process.cwd(), showAll, onePerLine);
+        return;
+    }
+    //If a directory is specified, list that directory
+    directories.forEach((arg, index) => {
+        try {
+            const stats = fs.statSync(arg);
+            if(stats.isDirectory()) {
+                //Print header if multiple directories are listed
+                if(directories.length > 1) console.log(`${arg}:`);
+
+                listDirectory(arg, showAll, onePerLine);
+                //add a blank line between directory listings if there are multiple directories
+                if(directories.length > 1 && index < directories.length - 1) console.log('');
+            } else{
+                console.log(arg);// single file
+            }
+        } catch (error) {
+            console.error(`Error accessing ${arg}: ${error.message}`);
+        }
+    });
+}
+main();

implement-shell-tools/wc/wc.js

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+#!/usr/bin/env node
+const fs = require('node:fs');
+// Function to count lines, words, and bytes in a file
+function countFileContent(content) {
+    const lines = content.split('\n').length; // Count lines by splitting on newline characters
+    const words = content.trim().split(/\s+/).filter(Boolean).length; // Split by whitespace and filter out empty strings
+    const bytes = Buffer.byteLength(content, 'utf8');
+    return { lines, words, bytes };
+}
+
+//print counts in the format of wc according to options
+function printCounts(filePath, counts, options) {
+    const parts = [];
+    if(options.line) parts.push(counts.lines);
+    if(options.word) parts.push(counts.words);
+    if(options.byte) parts.push(counts.bytes);
+//if no specific count options are provided, print all counts
+    if(!options.line && !options.word && !options.byte) {
+    //default is to print all counts
+        parts.push(counts.lines, counts.words, counts.bytes);
+    }
+    console.log(parts.join('\t'),filePath);
+}
+
+function main() {
+    const args = process.argv.slice(2);
+    const options = {
+        line: false,
+        word: false,
+        byte: false,
+    };
+
+    //Separate options from file paths
+    const files = [];
+    args.forEach((arg) => {
+        if(arg === '-l') options.line = true;
+        else if(arg === '-w') options.word = true;
+        else if(arg === '-c') options.byte = true;
+        else files.push(arg);
+    });
+
+    if(files.length === 0) {
+        console.error('No files specified');
+        process.exit(1);
+    }
+
+    let totalCounts = { lines: 0, words: 0, bytes: 0 };
+    const multipleFiles = files.length > 1;
+
+    files.forEach(file => {
+        try {
+            const content = fs.readFileSync(file, 'utf-8');
+            const counts = countFileContent(content);
+
+            // Sum counts for total if multiple files
+            totalCounts.lines += counts.lines;
+            totalCounts.words += counts.words;
+            totalCounts.bytes += counts.bytes;
+
+            printCounts(file, counts, options);
+        } catch (error) {
+            console.error(`Error reading file ${file}: ${error.message}`);
+        }
+    });
+
+    // If multiple files, print total counts
+    if(multipleFiles) {
+        printCounts('total', totalCounts, options);
+    }
+}
+main();