Bun based system utility to handle pattern matching, sorting, and renaming files flawlessly in batch.

rename-files.ts

import { readdirSync } from "node:fs";
import { rename } from "node:fs/promises";
import { join } from "node:path";

const [searchPattern, replacePattern] = Bun.argv.slice(2);

if (!searchPattern || !replacePattern) {
  console.log("Usage:\n  bun rename-files.ts '<search_pattern>' '<replace_pattern>'");
  console.log("Example:\n  bun rename-files.ts 'Screenshot *.png' 'pic-*.png'");
  process.exit(1);
}

const currentDir = process.cwd();

// Fix: Split the pattern by '*' to get literal prefix and suffix strings
// e.g., "Screenshot *.png" -> prefix: "Screenshot ", suffix: ".png"
const parts = searchPattern.split("*");
const prefix = parts[0] || "";
const suffix = parts[1] || "";

console.log(`Working Directory: ${currentDir}`);
console.log(`Matching files starting with "${prefix}" and ending with "${suffix}"`);
console.log("--------------------------------------------");

const allFiles = readdirSync(currentDir, { withFileTypes: true });

// Filter files safely using pure string matching (case-insensitive)
const matchedFiles = allFiles
  .filter(entry => {
    if (!entry.isFile()) return false;
    const name = entry.name.toLowerCase();
    return name.startsWith(prefix.toLowerCase()) && name.endsWith(suffix.toLowerCase());
  })
  .map(entry => entry.name);

// Sort them in ascending sequence before numbering them
matchedFiles.sort((a, b) => a.localeCompare(b, undefined, { numeric: true, sensitivity: 'base' }));

if (matchedFiles.length === 0) {
  console.log("No files matched the pattern in this directory.");
  process.exit(0);
}

let count = 0;
for (let i = 0; i < matchedFiles.length; i++) {
  const file = matchedFiles[i];
  
  // Use the loop index + 1 as the counter string
  const counterStr = (i + 1).toString();
  const newFileName = replacePattern.replace("*", counterStr);
  
  console.log(`Renaming: ${file} -> ${newFileName}`);
  await rename(join(currentDir, file), join(currentDir, newFileName));
  count++;
}

console.log("--------------------------------------------");
console.log(`Successfully renamed ${count} file(s) in ascending order.`);