How do I fix a bad interpreter /bin/bash^M error?

The script was saved with CRLF line endings, so the shebang line carries a trailing carriage return. Convert the file to LF and save it again.

Can this tool detect mixed line endings?

Yes. It counts CRLF, LF and CR separately and warns explicitly when more than one kind is present in the same text.

Is my text sent to a server?

No. Detection and conversion run entirely in your browser with JavaScript string operations. No input is transmitted to any external server.

改行コード変換ツール (CRLF / LF / CR 相互変換・混在検出) | Line Ending Converter Online

How to Use the Line Ending Converter

A line break is not a single universal character. Windows terminates lines with two bytes, carriage return plus line feed (CRLF, 0D 0A). Unix, Linux and modern macOS use a bare line feed (LF, 0A). Classic Mac OS through version 9 used a bare carriage return (CR, 0D). Because the bytes differ, a file written on one platform can confuse tools on another — and the difference is completely invisible in most editors.

Paste text or load a file, and the tool reports how many of each ending it found, whether they are mixed, and how many lines there are. Choose a target ending and the converted text appears immediately, ready to copy or download. Turn on the symbol display to see exactly where each ␍ and ␊ sits.

Symptoms of the Wrong Line Ending

The classic one is bad interpreter: /bin/bash^M. A shell script saved on Windows carries a trailing CR on the shebang line, so the kernel looks for an interpreter literally named /bin/bash\r and fails. In Git, committing CRLF files into a repository that expects LF makes every line show as changed in a diff, burying the real edit. Some parsers also treat a stray CR as part of the last field, producing values with an invisible trailing character that never compare equal.

Mixed Endings

Mixed endings are the worst case: part of the file uses CRLF and part uses LF, usually because different editors touched it. Line counts disagree between tools, diffs become noisy, and search-and-replace behaves inconsistently. This tool flags mixing explicitly so you can normalize the whole file in one pass.

改行コード変換ツールの使い方

テキストを貼り付けるか、ファイルを読み込むと、CRLF・LF・CR がそれぞれ何個あるかを判定します。種類が混ざっている場合は警告を表示します。変換先を選ぶと即座に変換され、コピーまたはファイルとしてダウンロードできます。

「改行を記号で表示」をオンにすると、CR を ␍、LF を ␊ として可視化できます。どこに余分な CR が残っているかを目で確認したいときに使ってください。この記号は表示専用で、コピーやダウンロードの結果には含まれません。

よくある落とし穴と対処 / Common Pitfalls

落とし穴 / Pitfall	問題 / Problem	対処 / Fix
シェルスクリプトがCRLF Shell script saved as CRLF	bad interpreter: /bin/bash^M で起動しない The shebang gains a trailing CR	LFに変換して保存し直す Convert the file to LF
Gitで全行が差分になる Every line shows as changed in git diff	改行コードだけが変わり、実際の変更が埋もれる Real edits are buried in noise	.gitattributes で text=auto 等を宣言し git add --renormalize する Declare .gitattributes and renormalize
改行コードが混在する Mixed endings inside one file	ツールごとに行数が食い違い、置換結果も不安定になる Tools disagree on line counts	ファイル全体を一度に統一する(このツールの変換は全体に適用される) Normalize the whole file at once
末尾の改行の有無 Missing final newline	最終行に改行がないとPOSIXツールが最後の行を読み飛ばすことがある POSIX tools may skip an unterminated last line	変換前後で行数表示を見比べて、末尾改行の有無を意識する Check the line count before and after
CSVのフィールド内改行 Newlines inside quoted CSV fields	引用符で囲まれたフィールド内の改行まで一括変換するとデータの意味が変わる Blanket conversion also rewrites in-field newlines	CSVはCSVパーサ経由で扱う。単純な一括変換は避ける Use a CSV parser instead

言語別コード例 / Code Examples

JavaScript

// いったん LF に正規化してから目的の改行コードへ
const toLf = (s) => s.split("\r\n").join("\n").split("\r").join("\n");
const toCrlf = (s) => toLf(s).split("\n").join("\r\n");

Python

# newline="" で読み、実際の改行コードを保ったまま扱う
with open("in.txt", newline="") as f:
    body = f.read()
lf_only = body.replace("\r\n", "\n").replace("\r", "\n")

コマンドライン

# CRLF → LF
dos2unix target.sh

# Git で以後の混入を防ぐ(.gitattributes)
* text=auto
*.sh text eol=lf

バイト列の違い / Byte Comparison

"a" + 改行 + "b" のバイト列

  CRLF (Windows)   : 61 0D 0A 62   (4バイト)
  LF   (Unix/macOS): 61 0A 62      (3バイト)
  CR   (旧Mac)     : 61 0D 62      (3バイト)

同じ2行のテキストでも、改行コードが違えばバイト数もハッシュ値も変わります。

Why browser-only?

Files with line ending problems are usually source code, deployment scripts, or data exports — content you should not paste into an unknown server. This converter performs the replacement locally with plain string operations: nothing is uploaded, nothing is logged, and it works offline. Check the DevTools Network tab while converting — zero requests.

改行コードで困るのはソースコード・デプロイ用スクリプト・データエクスポートといった社外に出せないファイルがほとんどです。本ツールは変換がブラウザ内で完結し、外部送信は一切ありません。

Line Ending Converter