Convert Line Endings Between DOS And Unix In Emacs

Emacs handles line ending conversions through its buffer coding system. Whether you’re converting CRLF (DOS/Windows) to LF (Unix) or the reverse, the process is straightforward.

DOS to Unix (CRLF to LF)

Open the file in Emacs and run:

M-x set-buffer-file-coding-system RET undecided-unix

Or use the keyboard shortcut:

C-x RET f undecided-unix

Then save the file:

C-x C-s

The undecided-unix coding system strips carriage returns and normalizes to Unix line endings (LF only).

Unix to DOS (LF to CRLF)

For the reverse operation:

M-x set-buffer-file-coding-system RET undecided-dos

Or the shortcut:

C-x RET f undecided-dos

Save with C-x C-s.

Check Current Line Endings

Verify which line ending style a file uses by checking the mode line at the bottom of the Emacs window. The coding system appears in parentheses:

(Unix) — LF line endings
(DOS) — CRLF line endings
(Mac) — CR-only endings (legacy, rarely seen)

You can also query the coding system interactively:

M-x describe-current-coding-system

Batch Convert Multiple Files

For converting multiple files at once, use command-line utilities instead of opening each file in Emacs.

With dos2unix:

dos2unix file1.txt file2.txt file3.txt
unix2dos file1.txt file2.txt file3.txt

With sed:

sed -i 's/\r$//' file.txt      # DOS to Unix
sed -i 's/$/\r/' file.txt      # Unix to DOS

With perl:

perl -pi -e 's/\r\n/\n/g' file.txt   # DOS to Unix
perl -pi -e 's/\n/\r\n/g' file.txt   # Unix to DOS

With tr:

tr -d '\r' < file.txt > file.txt.tmp && mv file.txt.tmp file.txt   # DOS to Unix

Prevent Mixed Line Endings in Projects

Configure your project’s .gitattributes to enforce consistent line endings across team members:

* text=auto
*.txt text eol=lf
*.sh text eol=lf
*.bat text eol=crlf
*.ps1 text eol=crlf

The text=auto setting lets Git detect text files automatically. Specific rules override it — .sh files always use LF, .bat and PowerShell scripts use CRLF. This prevents line ending issues in version control regardless of each developer’s OS.

Configure Emacs for Consistent Defaults

To default new files to UTF-8 with Unix line endings, add this to your ~/.config/emacs/init.el (or ~/.emacs for older setups):

(setq buffer-file-coding-system 'utf-8-unix)
(setq default-buffer-file-coding-system 'utf-8-unix)

For projects that need DOS line endings by default:

(setq buffer-file-coding-system 'utf-8-dos)

You can also set coding per-mode or per-directory using .dir-locals.el:

((sh-mode . ((buffer-file-coding-system . utf-8-unix)))
 (batch-mode . ((buffer-file-coding-system . utf-8-dos))))

Handle Mixed Encodings and Line Endings

If you work with files that have mixed UTF-8/UTF-16 or inconsistent line endings, Emacs can detect and convert them. When opening a file, use:

M-x set-file-coding-system

Emacs will display available coding systems. Most common options:

utf-8-unix — UTF-8 with LF
utf-8-dos — UTF-8 with CRLF
utf-16-le — UTF-16 little-endian
iso-8859-1 — Latin-1

After converting, save with C-x C-s.

2026 Best Practices and Advanced Techniques

For Convert Line Endings Between DOS and Unix in Emacs, understanding both the fundamentals and modern practices ensures you can work efficiently and avoid common pitfalls. This guide extends the core article with practical advice for 2026 workflows.

Troubleshooting and Debugging

When issues arise, a systematic approach saves time. Start by checking logs for error messages or warnings. Test individual components in isolation before integrating them. Use verbose modes and debug flags to gather more information when standard output is not enough to diagnose the problem.

Performance Optimization

Monitor system resources to identify bottlenecks
Use caching strategies to reduce redundant computation
Keep software updated for security patches and performance improvements
Profile code before applying optimizations
Use connection pooling and keep-alive for network operations

Security Considerations

Security should be built into workflows from the start. Use strong authentication methods, encrypt sensitive data in transit, and follow the principle of least privilege for access controls. Regular security audits and penetration testing help maintain system integrity.

Related Tools and Commands

These complementary tools expand your capabilities:

Monitoring: top, htop, iotop, vmstat for system resources
Networking: ping, traceroute, ss, tcpdump for connectivity
Files: find, locate, fd for searching; rsync for syncing
Logs: journalctl, dmesg, tail -f for real-time monitoring
Testing: curl for HTTP requests, nc for ports, openssl for crypto

Integration with Modern Workflows

Consider automation and containerization for consistency across environments. Infrastructure as code tools enable reproducible deployments. CI/CD pipelines automate testing and deployment, reducing human error and speeding up delivery cycles.

Quick Reference

This extended guide covers the topic beyond the original article scope. For specialized needs, refer to official documentation or community resources. Practice in test environments before production deployment.