File Case Converter: Batch Rename for Uppercase, Lowercase & Title Case

Tools & Methods

• Shell (bash/zsh) scripts — lightweight for macOS/Linux and WSL on Windows.
• PowerShell — native on Windows, cross-platform via PowerShell Core.
• Python scripts — portable, great for complex rules and Unicode handling.
• Command-line utilities:
  • rename (Perl) — flexible on many Linux distros.
  • mmv — move/rename in bulk using patterns.
  • git mv — preserve history in repositories.
  • util-linux’s rename (sometimes different semantics).
• Batch tools & GUI apps — e.g., Bulk Rename Utility (Windows), pyRenamer (Linux), Finder/Automator workflows (macOS).

Example Scripts (preserve extensions)

• Bash (lowercase filenames):

bash
 ffON2NH02oMAcqyoh2UU MQCbz04ET5EljRmK3YpQ CPXAhl7VTkj2dHDyAYAf” data-copycode=“true” role=“button” aria-label=“Copy Code”>Copy CodeCopied
#!/bin/bash
shopt -s nullglob for f in; do
  [ -f “\(f</span><span class="token" style="color: rgb(163, 21, 21);">"</span><span> </span><span class="token" style="color: rgb(57, 58, 52);">]</span><span> </span><span class="token" style="color: rgb(57, 58, 52);">||</span><span> </span><span class="token builtin" style="color: rgb(43, 145, 175);">continue</span><span> </span><span>  </span><span class="token assign-left" style="color: rgb(54, 172, 170);">ext</span><span class="token" style="color: rgb(57, 58, 52);">=</span><span class="token" style="color: rgb(163, 21, 21);">"</span><span class="token" style="color: rgb(54, 172, 170);">\){f##.}”
  name=“${f%.}”
  new=“\((</span><span class="token builtin" style="color: rgb(43, 145, 175);">echo</span><span class="token" style="color: rgb(54, 172, 170);"> </span><span class="token" style="color: rgb(54, 172, 170);">"</span><span class="token" style="color: rgb(54, 172, 170);">\)name” | tr ’[:upper:]’ ’[:lower:]’).\({ext</span><span class="token" style="color: rgb(57, 58, 52);">,,</span><span class="token" style="color: rgb(54, 172, 170);">}</span><span class="token" style="color: rgb(163, 21, 21);">"</span><span> </span><span>  </span><span class="token" style="color: rgb(0, 0, 255);">if</span><span> </span><span class="token" style="color: rgb(57, 58, 52);">[</span><span> </span><span class="token" style="color: rgb(163, 21, 21);">"</span><span class="token" style="color: rgb(54, 172, 170);">\)f“ != ”\(new</span><span class="token" style="color: rgb(163, 21, 21);">"</span><span> </span><span class="token" style="color: rgb(57, 58, 52);">]</span><span class="token" style="color: rgb(57, 58, 52);">;</span><span> </span><span class="token" style="color: rgb(0, 0, 255);">then</span><span> </span><span class="token" style="color: rgb(57, 58, 52);">mv</span><span> -i -- </span><span class="token" style="color: rgb(163, 21, 21);">"</span><span class="token" style="color: rgb(54, 172, 170);">\)f“ ”\(new</span><span class="token" style="color: rgb(163, 21, 21);">"</span><span class="token" style="color: rgb(57, 58, 52);">;</span><span> </span><span class="token" style="color: rgb(0, 0, 255);">fi</span><span> </span><span></span><span class="token" style="color: rgb(0, 0, 255);">done</span><span> </span></code></div></div></pre> <ul> <li>PowerShell (convert to snake_case):</li> </ul> <pre><div class="XG2rBS5V967VhGTCEN1k"><div class="nHykNMmtaaTJMjgzStID"><div class="HsT0RHFbNELC00WicOi8"><i><svg width="16" height="16" fill="none" xmlns="http://www.w3.org/2000/svg"><path fill="currentColor" fill-rule="evenodd" clip-rule="evenodd" d="M15.434 7.51c.137.137.212.311.212.49a.694.694 0 0 1-.212.5l-3.54 3.5a.893.893 0 0 1-.277.18 1.024 1.024 0 0 1-.684.038.945.945 0 0 1-.302-.148.787.787 0 0 1-.213-.234.652.652 0 0 1-.045-.58.74.74 0 0 1 .175-.256l3.045-3-3.045-3a.69.69 0 0 1-.22-.55.723.723 0 0 1 .303-.52 1 1 0 0 1 .648-.186.962.962 0 0 1 .614.256l3.541 3.51Zm-12.281 0A.695.695 0 0 0 2.94 8a.694.694 0 0 0 .213.5l3.54 3.5a.893.893 0 0 0 .277.18 1.024 1.024 0 0 0 .684.038.945.945 0 0 0 .302-.148.788.788 0 0 0 .213-.234.651.651 0 0 0 .045-.58.74.74 0 0 0-.175-.256L4.994 8l3.045-3a.69.69 0 0 0 .22-.55.723.723 0 0 0-.303-.52 1 1 0 0 0-.648-.186.962.962 0 0 0-.615.256l-3.54 3.51Z"></path></svg></i><p class="li3asHIMe05JPmtJCytG wZ4JdaHxSAhGy1HoNVja cPy9QU4brI7VQXFNPEvF">powershell</p></div><div class="CF2lgtGWtYUYmTULoX44"><button type="button" class="st68fcLUUT0dNcuLLB2_ ffON2NH02oMAcqyoh2UU MQCbz04ET5EljRmK3YpQ CPXAhl7VTkj2dHDyAYAf" data-copycode="true" role="button" aria-label="Copy Code"><svg viewBox="0 0 16 16" fill="none" xmlns="http://www.w3.org/2000/svg"><path fill="currentColor" fill-rule="evenodd" clip-rule="evenodd" d="M9.975 1h.09a3.2 3.2 0 0 1 3.202 3.201v1.924a.754.754 0 0 1-.017.16l1.23 1.353A2 2 0 0 1 15 8.983V14a2 2 0 0 1-2 2H8a2 2 0 0 1-1.733-1H4.183a3.201 3.201 0 0 1-3.2-3.201V4.201a3.2 3.2 0 0 1 3.04-3.197A1.25 1.25 0 0 1 5.25 0h3.5c.604 0 1.109.43 1.225 1ZM4.249 2.5h-.066a1.7 1.7 0 0 0-1.7 1.701v7.598c0 .94.761 1.701 1.7 1.701H6V7a2 2 0 0 1 2-2h3.197c.195 0 .387.028.57.083v-.882A1.7 1.7 0 0 0 10.066 2.5H9.75c-.228.304-.591.5-1 .5h-3.5c-.41 0-.772-.196-1-.5ZM5 1.75v-.5A.25.25 0 0 1 5.25 1h3.5a.25.25 0 0 1 .25.25v.5a.25.25 0 0 1-.25.25h-3.5A.25.25 0 0 1 5 1.75ZM7.5 7a.5.5 0 0 1 .5-.5h3V9a1 1 0 0 0 1 1h1.5v4a.5.5 0 0 1-.5.5H8a.5.5 0 0 1-.5-.5V7Zm6 2v-.017a.5.5 0 0 0-.13-.336L12 7.14V9h1.5Z"></path></svg>Copy Code</button><button type="button" class="st68fcLUUT0dNcuLLB2_ WtfzoAXPoZC2mMqcexgL ffON2NH02oMAcqyoh2UU MQCbz04ET5EljRmK3YpQ GnLX_jUB3Jn3idluie7R"><svg fill="none" viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"><path fill="currentColor" fill-rule="evenodd" d="M20.618 4.214a1 1 0 0 1 .168 1.404l-11 14a1 1 0 0 1-1.554.022l-5-6a1 1 0 0 1 1.536-1.28l4.21 5.05L19.213 4.382a1 1 0 0 1 1.404-.168Z" clip-rule="evenodd"></path></svg>Copied</button></div></div><div class="mtDfw7oSa1WexjXyzs9y" style="color: var(--sds-color-text-01); font-family: var(--sds-font-family-monospace); direction: ltr; text-align: left; white-space: pre; word-spacing: normal; word-break: normal; font-size: var(--sds-font-size-label); line-height: 1.2em; tab-size: 4; hyphens: none; padding: var(--sds-space-x02, 8px) var(--sds-space-x04, 16px) var(--sds-space-x04, 16px); margin: 0px; overflow: auto; border: none; background: transparent;"><code class="language-powershell" style="color: rgb(57, 58, 52); font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace; direction: ltr; text-align: left; white-space: pre; word-spacing: normal; word-break: normal; font-size: 0.9em; line-height: 1.2em; tab-size: 4; hyphens: none;"><span class="token" style="color: rgb(57, 58, 52);">Get-ChildItem</span><span> </span><span class="token" style="color: rgb(57, 58, 52);">-</span><span>File </span><span class="token" style="color: rgb(57, 58, 52);">|</span><span> </span><span class="token" style="color: rgb(57, 58, 52);">ForEach-Object</span><span> </span><span class="token" style="color: rgb(57, 58, 52);">{</span><span> </span><span>  </span><span class="token" style="color: rgb(54, 172, 170);">\)ext = \(_</span><span class="token" style="color: rgb(57, 58, 52);">.</span><span>Extension </span><span>  </span><span class="token" style="color: rgb(54, 172, 170);">\)name = \(_</span><span class="token" style="color: rgb(57, 58, 52);">.</span><span>BaseName </span><span>  </span><span class="token" style="color: rgb(54, 172, 170);">\)new = (\(name</span><span> </span><span class="token" style="color: rgb(57, 58, 52);">-replace</span><span> </span><span class="token" style="color: rgb(163, 21, 21);">'[^\w]+'</span><span class="token" style="color: rgb(57, 58, 52);">,</span><span class="token" style="color: rgb(163, 21, 21);">'_'</span><span class="token" style="color: rgb(57, 58, 52);">)</span><span class="token" style="color: rgb(57, 58, 52);">.</span><span>ToLower</span><span class="token" style="color: rgb(57, 58, 52);">(</span><span class="token" style="color: rgb(57, 58, 52);">)</span><span> </span><span class="token" style="color: rgb(57, 58, 52);">+</span><span> </span><span class="token" style="color: rgb(54, 172, 170);">\)ext
  if (\(_</span><span class="token" style="color: rgb(57, 58, 52);">.</span><span>Name </span><span class="token" style="color: rgb(57, 58, 52);">-ne</span><span> </span><span class="token" style="color: rgb(54, 172, 170);">\)new) { Rename-Item -LiteralPath \(_</span><span class="token" style="color: rgb(57, 58, 52);">.</span><span>FullName </span><span class="token" style="color: rgb(57, 58, 52);">-</span><span>NewName </span><span class="token" style="color: rgb(54, 172, 170);">\)new -WhatIf }
}

(remove -WhatIf to execute)

• Python (title case, handle Unicode):

python
Copy CodeCopied
import os, unicodedata def title_case(s): return ’ ‘.join(w.capitalize() for w in s.split())
for fname in os.listdir(’.’):
    if os.path.isfile(fname):
        name, ext = os.path.splitext(fname)
        new = title_case(name) + ext         if new != fname:
            os.rename(fname, new)

Best Practices

• Always test first: Run with dry-run flags (e.g., -WhatIf) or print proposed changes before renaming.
• Preserve extensions: Treat the extension separately to avoid breaking file types.
• Handle collisions: Detect existing target names and decide to skip, append suffixes, or prompt.
• Backup or use version control: Keep a backup or operate in a git repo so changes can be reverted.
• Respect file metadata: Renaming typically preserves timestamps, but check if your tool alters metadata.
• Unicode & normalization: Normalize filenames (NFC/NFD) when moving between macOS and Linux to avoid duplicates.
• Permissions & ownership: Run with appropriate permissions; avoid running mass-rename as root unless necessary.
• Recursive options: Use recursive renaming carefully; exclude system directories and hidden files unless intended.

Tips for Specific Cases

• Convert to snake_case: replace non-alphanumeric with underscores, collapse multiple underscores, trim edges.
• Convert camelCase to words: insert separators before capital letters then lowercase.
• Keep leading dots (hidden files) intact when operating on Unix-like systems.
• For mixed-case preservation (e.g., acronyms), create rule sets or mapping tables.

Quick Workflow (recommended)

1. Scan: List files and show proposed new names.
2. Dry-run: Execute script with dry-run flag or print-only mode.
3. Backup: Commit to git or copy files to backup folder.
4. Execute: Perform renaming.
5. Verify: Check for collisions, broken references, or issues.

If you want, I can generate a ready-to-run script tailored to your OS and desired naming convention.