This note outlines three quick methods—using dos2unix, sed, or an editor conversion—to ensure the script runs without errors.

When you run a shell script on a Unix-like system and see an error like:

zsh: ./script.sh: bad interpreter: /bin/bash^M: no such file or directory

this indicates that your script was saved with Windows line endings (CRLF) instead of Unix line endings (LF). The extra ^M character causes the interpreter path to be misread.

Why It Happens

  • Windows vs. Unix: Windows uses CRLF (\r\n) for line breaks, while Unix-like systems use LF (\n).
  • Impact on Scripts: The extra carriage return (\r) is appended to the shebang line (e.g., /bin/bash^M), causing the system to fail in locating the correct interpreter.

How to Fix It

  1. Using dos2unix

If you have dos2unix installed, simply run:

dos2unix script.sh

This command converts the file to Unix line endings.

  1. Using sed

You can also remove carriage returns using sed:

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

This command edits the file in place, removing the \r at the end of each line.

  1. Using a Text Editor

Open the script in an editor that supports different line endings (e.g., VS Code, Sublime Text, or Notepad++), and convert the file format to Unix (LF). Save the file afterwards.

By ensuring your shell scripts use Unix line endings, you can avoid interpreter errors and ensure smooth execution across different environments.