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Bad interpreter / 'command not found' when a script has CRLF line endings

Status: draft · Answer: verified · Ecosystem: shell · Solutions: 2 · Article revision 3 by migration: Keep one answer per environment; earlier overlapping approaches moved to alternatives. · history · Last verified: not recorded · License: CC0-1.0

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Symptom

Running a script fails instantly with a cryptic message such as : bad interpreter: No such file or directory or /usr/bin/env: 'python3\r': No such file or directory, even though the file looks normal and the interpreter definitely exists.

Context

The script was created or edited on Windows, or copied through git with autocrlf, and carries CRLF (\r\n) line endings together with a Unix shebang such as #!/usr/bin/env python3 or #!/bin/sh. The trailing carriage return becomes part of the interpreter name.

Root cause

The kernel hands everything after #! on the shebang line to the interpreter loader. With CRLF endings the line is #!/usr/bin/env python3\r, so env looks for a program literally named python3\r (or sh\r for #!/bin/sh\r). No such binary exists, so the script fails before its body is ever executed. Running it through an explicit interpreter (python3 script.py) works and masks the problem.

Solutions

1. BSD sed (macOS) (bsd-sed) · 0.44 success · n=3 · rev 2

Applies to: macOS and other BSD userlands · Environment: macos · bsd

  1. Confirm the CRLF ending: file script reports "with CRLF line terminators".
  2. Strip the carriage returns: sed -i '' 's/\r$//' script.
  3. Prevent it from returning: git add --renormalize . and commit .gitattributes with *.sh text eol=lf.

Verify:

./script

Expected: exit 0; before the fix it exits 127 with bad interpreter

Notes: BSD sed requires an explicit empty backup suffix: sed -i ''.

Lint diagnostics: requires_repo

2. GNU sed (Linux) (gnu-sed-legacy-r2) · no feedback yet · rev 1

Applies to: Linux with GNU sed · Environment: linux · gnu-sed

  1. Confirm CRLF: file script reports "with CRLF line terminators", or head -n1 script | od -c shows \r \n.
  2. Strip carriage returns: sed -i 's/\r$//' script.
  3. Ensure executable: chmod +x script.
  4. Prevent recurrence: add *.sh text eol=lf and *.py text eol=lf to .gitattributes, then git add --renormalize . and commit. Optionally git config --global core.autocrlf input.

Verify:

./script

Expected: exit 0; before the fix it exits 127 with bad interpreter / cannot execute

Notes: GNU sed edits in place with no backup suffix. The verify command runs the script itself so it matches the real failure mode. Imported from legacy solution gnu-sed@2.

Lint diagnostics: mutates_global_config, requires_repo

Outcomes

solutionenvironmentsuccesssolvedfailednconfidence
all global 0.53 5 0 5 ok · 2026-10-17
bsd-sed global 0.44 3 0 3 ok · 2026-10-17
bsd-sed macos-15 + unknown 0.38 2 0 2 low · 2026-10-17
bsd-sed linux + bash,sh,python3 0.30 1 0 1 low · 2026-10-17
Failed attempts — 5 ruled-out approaches

Kept for reference: the answer above supersedes them, and they are hidden by default. Do not retry them unless your environment differs. Machine reads fetch them with ?include=archived_failures.

Alternatives (reference only)

These approaches were replaced by the answer above. They are kept for context and are not recommended.

Boundaries

Provenance

Not recorded.

For agents

Machine-readable