🐧 dos2unix: How to Fix Broken Shell Scripts

If you’ve ever written a Bash script on Windows and then tried to run it on Linux, chances are you’ve seen cryptic errors like:

-bash: ./script1.sh: cannot execute: required file not found

or

bash: ./script1.sh: /bin/bash^M: bad interpreter: No such file or directory

What happened? Windows sabotaged your script—or more precisely, you did. By default, Windows editors save files with CRLF (\r\n) line endings, while Unix systems expect just LF (\n). That invisible \r (carriage return) completely wrecks interpreters, conditionals, and redirects.

Installing dos2unix

The easiest way to fix this is with the dos2unix tool:

• Ubuntu / Debian:

sudo apt update
sudo apt install dos2unix

• Macos

brew install dos2unix

Check it’s installed:

dos2unix --version

Fixing Your Script

Once installed, just run:

dos2unix fuckedupscript.sh

This strips out all the \r characters, and your script should run normally.

No dos2unix? No Problem

If you can’t install it, there are alternatives:

• sed

sed -i 's/\r$//' file.sh

• tr

tr -d '\r' < file.sh > fixed.sh && mv fixed.sh file.sh

Preventing the Mess

Best fix: avoid the problem altogether.

• Use an editor that can save files in Unix (LF) format.
• If you use Git, set these global configs to ensure CRLF is converted to LF on commit:

git config --global core.autocrlf input
git config --global core.eol lf

With this, your scripts won’t randomly break just because you switched systems.\

Epilog

CRLF vs LF is one of those tiny differences that cause big headaches. The good news is once you know the cause, the fix is simple—and with the right Git or editor settings, you’ll never have to “un-fuck” a script again.