Write tool creates files with CRLF line endings on WSL2/Linux, breaking shell script execution

Environment:

• Claude Code version: Current (as of 2025-01-02)
• OS: Linux (WSL2: Linux 6.6.87.2-microsoft-standard-WSL2)
• Platform: linux (from environment context)

Description:

The Write tool creates files with Windows-style CRLF (\r\n) line endings even when running on Linux/WSL2 systems. This causes bash scripts to fail immediately after creation with errors like:

/bin/bash: line 1: ./script.sh: cannot execute: required file not found

Reproduction Steps:

1. Use Write tool to create a bash script on WSL2/Linux:

<invoke name="Write">
<parameter name="file_path">/path/to/test.sh</parameter>
<parameter name="content">#!/bin/bash
echo "Hello World"
</parameter>
</invoke>

1. Verify line endings:

file test.sh
# Shows: ASCII text, with CRLF line terminators

od -c test.sh | head -2
# Shows \r\n instead of \n

1. Attempt to execute:

chmod +x test.sh
./test.sh
# Error: required file not found (due to \r in shebang)

Expected Behavior:

On Unix-like systems (Linux, macOS, WSL), the Write tool should:

• Create files with LF (\n) line endings by default
• Respect the platform's native line ending convention
• Alternatively, provide a parameter to specify line ending style

Current Workaround:

After every Write operation creating shell scripts:

dos2unix script.sh
# or: sed -i 's/\r$//' script.sh

Impact:

• Immediate execution failures: Scripts cannot be tested immediately after creation without manual post-processing
• Workflow friction: Requires extra steps after file creation
• Easy to forget: The error only appears when attempting to execute the script
• Partial mitigation via .gitattributes: Using .gitattributes normalizes line endings at commit time, but doesn't help the window between file creation and commit

Suggested Solution:

The Write tool should detect the platform and use appropriate line endings:

• Unix-like systems → LF (\n)
• Windows (non-WSL) → CRLF (\r\n)
• Optionally: Allow explicit line ending specification via parameter

Additional Context:

This issue affects any text file creation but is most critical for shell scripts where CRLF breaks the shebang (#!/bin/bash\r is not recognized). Similar issues may affect other interpreted scripts (Python, Ruby, etc.) though they're often more tolerant of CRLF.