Return symbol

如何看到換行符號、如何從文章中取代換行符號 (英文：Return symbol, line terminators, line endings, newline, end of line (EOL), line feed (LF) or line break)。

• On Win : CRLF = \r\n
• On Unix, Linux & recent versions of macOS : LF = \n
• On classic versions of macOS e.g. Mac OS 9: CR = \r

如何使用編輯軟體，看到換行符號

查看每一行使用的換行符號

• Notepad++ On Win 選單 → 檢視 → 特殊字元 → 顯示行尾字元 (EOL)
• RawLineEdit for Sublime text
  • 換行符號是 CRLF = \r\n 每行最後顯示的是 <0x0d>¬
  • 換行符號是 LF = \n 每行最後顯示的是 ¬ 象形符號 (glyph)
  • 換行符號是 CR = \r 每行最後顯示的是 <0x0d>
• BASH cat command e.g. cat -e <filename>
  • 換行符號是 CRLF = \r\n 每行最後顯示的是 ^M$
  • 換行符號是 LF = \n 每行最後顯示的是 $
  • 換行符號是 CR = \r 每行最後顯示的是 ^M

查看檔案使用的換行符號

• atom/line-ending-selector: Switch between Unix and Window style line endings. for Atom on Win , macOS & Linux
• file (command): file filename.txt on Linux , macOS & Cygwin on Win

檔案內容	File command 偵測結果
換行符號是 CRLF = \r\n	UTF-8 Unicode text, with CRLF line terminators
換行符號是 LF = \n	UTF-8 Unicode text
換行符號是 CR = \r	UTF-8 Unicode text, with CR line terminators
特例: 換行符號夾雜 \r\n 和 \r	UTF-8 Unicode text, with CRLF, CR line terminators
特例: 換行符號夾雜 \r\n 和 \n	UTF-8 Unicode text, with CRLF, LF line terminators
特例: 換行符號夾雜 \n 和 \r	UTF-8 Unicode text, with CR, LF line terminators
特例: 無內容的空檔案	empty

不同換行符號 在不同作業系統的編輯器看到的文件狀況

檔案內容	Windows 10 內建「記事本」	Windows 10 免費編輯器 Notepad++ v. 7.5.9	Mac 內建「文字編輯.app」	Mac 編輯器 Sublime Text v. 3.2
換行符號是 CRLF = \r\n	ok	ok	ok	ok
換行符號是 LF = \n	預期不同行的內容擠在一起	ok	ok	ok
換行符號是 CR = \r	預期不同行的內容擠在一起	ok	ok	ok

計算換行符號的數量

## 計算 \n (不包含 \r\n) 換行符號的數量
% perl -ne '$count++ if /[^\r]\n/; END{print "純 LF 數量: $count\n"}' YOUR_FILE.txt

## 計算 \r\n 換行符號的數量
% perl -ne '$count++ if /\r\n/; END{print "CRLF 數量: $count\n"}' YOUR_FILE.txt

如何取代換行符號

• 支援 Regular expression 的文字編輯軟體，例: 將Email清單，轉成Email軟體可以使用的寄信名單 (取代換行符號為逗號)
• MySQL: SELECT REPLACE(REPLACE(REPLACE(`column`,'\r\n',''),'\n',''),'\r','') or SELECT TRIM(REPLACE(`column`, '\n','' ))

• Excel:
  • =CLEAN(A1) Use the CLEAN function to "remove the first 32 nonprinting characters in the 7-bit ASCII code (values 0 through 31) from the text". Meanwhile, the return symbol will be removed from the text.
  • =TRIM(SUBSTITUTE(SUBSTITUTE(A1, CHAR(13),""), CHAR(10),", ") to replace the return symbol in the cell located at A1 .
    • CHAR(10) means "Line feed" which equal to \n
    • CHAR(13) means "Carriage return" which equal to \r

• Python way: How can I remove a trailing newline in Python? - Stack Overflow [Last visited: 2019-06-14]

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• Url encoding of \r\n is %0D%0A. More details on HTML URL Encoding Reference