Implementing shell tools so that they behave like the real versions on a typical system: cat, ls, and wc.

Author: Emilianouz

implement-shell-tools/cat/cat-commander.js

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+import { program } from "commander";
+import { promises as fs } from "node:fs";
+import process from "node:process";
+
+program
+    .name("read-files-content")
+    .description("Read the content of a file (simulating cat command)")
+    .option("-n, --number","Number of lines")
+    .option("-b","Number of no-blanks lines")
+    .argument("<path...>","The file path to process"); //file
+
+program.parse();
+
+const argv = program.args;
+
+if (argv.length === 0) {
+    console.error(`Expected file path(s),passed but got ${argv.length}.`);
+    process.exit(1);
+}
+
+//const path = argv[0];
+for (const path of argv){
+    const option = program.opts();
+    const content = await fs.readFile(path, "utf-8");
+    if (option.number){
+        // split content
+        let lines = content.split(/\n/);
+        // removes last line
+        if (lines[lines.length - 1] === ""){
+            lines = lines.slice(0,-1);
+        }
+        lines
+            .map((line,index) => `${(index + 1).toString().padStart(6)}\t${line}`)
+            .forEach(line => console.log(line))
+
+        } else if (option.b){
+            let lines = content.split("\n");
+            let linesCounter = 0;
+            if (lines[lines.length - 1] === ""){
+                lines = lines.slice(0,-1);
+            }
+            lines
+            .map((line) => {
+                if (line.trim().length > 0) { 
+                    linesCounter++;
+                    return `${linesCounter.toString().padStart(6)}\t${line}`
+                }else{
+                    return `${line}`
+                    }}
+                )
+            .forEach(line => console.log(line))
+        }else {
+            const output = content.endsWith("\n") ? content.slice(0,-1) : content;
+            console.log(output);
+    }
+}

implement-shell-tools/ls/ls-commander.js

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+import { program } from "commander";
+import { promises as fs } from "node:fs";
+import process from "node:process";
+
+program 
+    .name("list-files")
+    .description("List files in a directory")
+    .option("-1", "Show line by line")
+    .option("-a, --all", "Show hidden files")
+    .argument("[paths...]", "The directory paths",["."]);
+
+program.parse();
+
+const argv = program.args;
+
+if (argv.length != 1){
+    console.error(`Expected exactly 1 argument (a path) to be passed but got ${argv.length}`);
+    process.exit(1);
+}
+const dirPath = argv[0];
+const options = program.opts();
+
+const entries = await fs.readdir(dirPath)
+
+const listFiles = entries.map((entry) => `${entry.padStart(6)}` )
+const noHidden = listFiles.filter(name => !name.startsWith('.'));
+
+if (options.all && options[1]){
+    console.log(listFiles.join('\n'));
+} else if (options.all) {
+    console.log(listFiles.join(' '));
+} else if (options[1]){
+    console.log(noHidden.join('\n'));
+} else {
+    console.log(noHidden.join(' '));
+}

implement-shell-tools/wc/wc-commander.js

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+import {program} from "commander";
+import { promises as fs } from "node:fs";
+import process from "node:process";
+import { glob } from "glob";
+
+program
+    .name("content counter")
+    .description("Counts lines, words, or characters in a file or files of a directory.")
+    .option("-l,--lines","Options for l:Lines.")
+    .option("-w,--words","Options for w:words.")
+    .option("-c","Options for c:characters.")
+    .argument("<path...>","The file or directory to process");
+
+program.parse();
+
+const argv = program.args;
+
+const options = program.opts();
+
+const result = []; 
+let totalLines = 0;
+let totalWords = 0;
+let totalChars = 0;
+
+for (const file of argv){
+
+  //1.  Read each file
+
+  const content = await fs.readFile(file,"utf-8");
+  // 2. calculate values
+  const lines = content.split(/\n/g).length - 1 ;
+  const words = content.trim().split(/\s+/).length;
+  const chars = content.split("").length;
+  // variable to pile up final line results according options
+  const thisLine = [];
+  if (options.lines){ thisLine.push(lines.toString().padStart(8)) };
+  if (options.words){ thisLine.push(words.toString().padStart(8)) };
+  if (options.c){ thisLine.push(chars.toString().padStart(8)) };
+  if (!options.lines && !options.words && !options.c){ thisLine.push(lines.toString().padStart(8),words.toString().padStart(8),chars.toString().padStart(8)) };
+  result.push(`${thisLine.join("")} ${file}`)
+  // 3. add results 
+  // variables to accumulate the total
+  totalLines += lines;
+  totalWords += words;
+  totalChars += chars;
+// 4. add total results if several files
+}
+if (argv.length>1){
+  const finalLine = [];
+  finalLine.push(totalLines.toString().padStart(8)),
+  finalLine.push(totalWords.toString().padStart(8)),
+  finalLine.push(totalChars.toString().padStart(8));
+  result.push(`${finalLine.join("")} total`)
+}
+// 5. show results
+const output = result.join('\n');
+console.log(output)
+
+
+
+