Editing 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}}: {{kbd | key=<nowiki>CRLF</nowiki>}} = {{kbd | key=<nowiki>\r\n</nowiki>}}
* On Unix, {{Linux}} & recent versions of {{Mac}}: {{kbd | key=<nowiki>LF</nowiki>}} = {{kbd | key=<nowiki>\n</nowiki>}}
* On classic versions of {{Mac}}<ref>[https://en.wikipedia.org/wiki/Classic_Mac_OS Classic Mac OS - Wikipedia]</ref><ref>[https://en.wikipedia.org/wiki/Newline Newline - Wikipedia]</ref> e.g. Mac OS 9: {{kbd | key=<nowiki>CR</nowiki>}} = {{kbd | key=<nowiki>\r</nowiki>}}

== 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
* [https://notepad-plus-plus.org/zh/ Notepad++] On {{Win}} 選單 → 檢視 → 特殊字元 → 顯示行尾字元 (EOL)
* [https://github.com/facelessuser/RawLineEdit RawLineEdit] for [https://www.sublimetext.com/ Sublime text]
** 換行符號是 {{kbd | key=<nowiki>CRLF</nowiki>}} = {{kbd | key=<nowiki>\r\n</nowiki>}} 每行最後顯示的是 {{kbd | key=<nowiki><0x0d>¬</nowiki>}}
** 換行符號是 {{kbd | key=<nowiki>LF</nowiki>}} = {{kbd | key=<nowiki>\n</nowiki>}} 每行最後顯示的是 {{kbd | key=<nowiki>¬</nowiki>}} 象形符號 (glyph)
** 換行符號是 {{kbd | key=<nowiki>CR</nowiki>}} = {{kbd | key=<nowiki>\r</nowiki>}} 每行最後顯示的是 {{kbd | key=<nowiki><0x0d></nowiki>}}
* BASH [http://www.linfo.org/cat.html cat] command e.g. {{kbd | key=<nowiki>cat -e <filename></nowiki>}}
** 換行符號是 {{kbd | key=<nowiki>CRLF</nowiki>}} = {{kbd | key=<nowiki>\r\n</nowiki>}} 每行最後顯示的是 {{kbd | key=<nowiki>^M$</nowiki>}}
** 換行符號是 {{kbd | key=<nowiki>LF</nowiki>}} = {{kbd | key=<nowiki>\n</nowiki>}} 每行最後顯示的是 {{kbd | key=<nowiki>$</nowiki>}}
** 換行符號是 {{kbd | key=<nowiki>CR</nowiki>}} = {{kbd | key=<nowiki>\r</nowiki>}} 每行最後顯示的是 {{kbd | key=<nowiki>^M</nowiki>}}

查看檔案使用的換行符號
* [https://github.com/atom/line-ending-selector atom/line-ending-selector: Switch between Unix and Window style line endings.] for [https://atom.io/ Atom] on {{Win}}, {{Mac}} & {{Linux}}
* [https://en.wikipedia.org/wiki/File_(command) file (command)]: {{kbd | key=<nowiki>file filename.txt</nowiki>}} on {{Linux}}, {{Mac}}<ref>[https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man1/file.1.html file(1) Mac OS X Manual Page]</ref> & Cygwin on {{Win}}

<table border="1" class="wikitable" >
<tr>
<th>檔案內容</th>
<th>File command 偵測結果</th>
</tr>

<tr>
<td>換行符號是 {{kbd | key=<nowiki>CRLF</nowiki>}} = {{kbd | key=<nowiki>\r\n</nowiki>}}</td>
<td>UTF-8 Unicode text, with CRLF line terminators</td>
</tr>
<tr>

<td>換行符號是 {{kbd | key=<nowiki>LF</nowiki>}} = {{kbd | key=<nowiki>\n</nowiki>}}</td>
<td>UTF-8 Unicode text {{exclaim}}</td>
</tr>

<tr>
<td>換行符號是 {{kbd | key=<nowiki>CR</nowiki>}} = {{kbd | key=<nowiki>\r</nowiki>}}</td>
<td>UTF-8 Unicode text, with CR line terminators</td>
</tr>

<tr>
<td>特例: 換行符號夾雜 {{kbd | key=<nowiki>\r\n</nowiki>}} 和 {{kbd | key=<nowiki>\r</nowiki>}}</td>
<td>UTF-8 Unicode text, with CRLF, CR line terminators</td>
</tr>

<tr>
<td>特例: 換行符號夾雜 {{kbd | key=<nowiki>\r\n</nowiki>}} 和 {{kbd | key=<nowiki>\n</nowiki>}}</td>
<td>UTF-8 Unicode text, with CRLF, LF line terminators</td>
</tr>

<tr>
<td>特例: 換行符號夾雜 {{kbd | key=<nowiki>\n</nowiki>}} 和 {{kbd | key=<nowiki>\r</nowiki>}}</td>
<td>UTF-8 Unicode text, with CR, LF line terminators</td>
</tr>

<tr>
<td>特例: 無內容的空檔案</td>
<td>empty</td>
</tr>

</table>

== 不同換行符號 在不同作業系統的編輯器看到的文件狀況 ==

<table border="1" class="wikitable" >
<tr>
<th>檔案內容</th>
<th>Windows 10 內建「記事本」</th>
<th>Windows 10 免費編輯器 [https://notepad-plus-plus.org/zh/ Notepad++] v. 7.5.9</th>
<th>Mac 內建「[https://support.apple.com/zh-tw/guide/textedit/welcome/mac 文字編輯.app]」</th>
<th>Mac 編輯器 [https://www.sublimetext.com/ Sublime Text] v. 3.2</th>
</tr>

<tr>
<td>換行符號是 {{kbd | key=<nowiki>CRLF</nowiki>}} = {{kbd | key=<nowiki>\r\n</nowiki>}}</td>
<td>ok</td>
<td>ok</td>
<td>ok</td>
<td>ok</td>
</tr>
<tr>

<td>換行符號是 {{kbd | key=<nowiki>LF</nowiki>}} = {{kbd | key=<nowiki>\n</nowiki>}}</td>
<td>{{exclaim}} 預期不同行的內容擠在一起</td>
<td>ok</td>
<td>ok</td>
<td>ok</td>
</tr>

<tr>
<td>換行符號是 {{kbd | key=<nowiki>CR</nowiki>}} = {{kbd | key=<nowiki>\r</nowiki>}}</td>
<td>{{exclaim}} 預期不同行的內容擠在一起</td>
<td>ok</td>
<td>ok</td>
<td>ok</td>
</tr>

</table>

== 計算換行符號的數量 ==

<pre>
## 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
</pre>

== 如何尋找與取代換行符號 ==

=== 文字編輯軟體如何取代換行符號 ===
* 支援 [[Regular expression]] 的文字編輯軟體，例: [[Regular expression#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) | 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 如何尋找換行符號 ===

<pre>
SELECT content,
       CASE 
           WHEN content LIKE CONCAT('%', CHAR(13), CHAR(10), '%') THEN 'CRLF (\\r\\n)'
           WHEN content LIKE CONCAT('%', CHAR(10), '%') THEN 'LF (\\n)'
           WHEN content LIKE CONCAT('%', CHAR(13), '%') THEN 'CR (\\r)'
           ELSE 'No newlines'
       END as newline_type
FROM my_table 
WHERE content REGEXP CONCAT('[', CHAR(10), CHAR(13), ']');
</pre>

=== MySQL 如何取代換行符號 ===

<ref> [https://stackoverflow.com/questions/13273343/replace-new-line-character-in-mysql-not-working sql - REPLACE new line character in MYSql not working - Stack Overflow] </ref><ref>[https://stackoverflow.com/questions/28368785/mysql-trim-both-whitespace-and-newline-characters MySQL: trim *both* whitespace and newline characters - Stack Overflow]</ref>

<pre>
UPDATE my_table
SET content = REPLACE(
    REPLACE(
        REPLACE(content, CONCAT(CHAR(13), CHAR(10)), ''),
        CHAR(10), ''
    ),
    CHAR(13), ''
)
WHERE content REGEXP CONCAT('[', CHAR(10), CHAR(13), ']');

-- or 

UPDATE my_table
SET `content` = REPLACE(REPLACE(REPLACE(`my_table`,'\r\n',''),'\n',''),'\r','')
;

</pre>

=== Excel 或 Google Sheet 如何尋找換行符號 ===
判斷是哪種換行符號：
<pre>
=IF(ISNUMBER(SEARCH(CHAR(13)&CHAR(10), A1)), "CRLF (\r\n)", 
  IF(ISNUMBER(SEARCH(CHAR(13), A1)), "CR (\r)", 
    IF(ISNUMBER(SEARCH(CHAR(10), A1)), "LF (\n)", 
      "無換行符號")))
</pre>

=== Excel 或 Google Sheet 如何取代換行符號 ===
For Microsoft Excel or Google Sheet
* {{kbd | key=<nowiki>=CLEAN(A1)</nowiki>}} Use the CLEAN function to "remove the first 32 nonprinting characters in the 7-bit ASCII code (values 0 through 31) from the text"<ref>[https://support.microsoft.com/en-us/office/clean-function-26f3d7c5-475f-4a9c-90e5-4b8ba987ba41 CLEAN function]</ref>. Meanwhile, the return symbol will be removed from the text. 
* {{kbd | key=<nowiki>=TRIM(SUBSTITUTE(SUBSTITUTE(A1, CHAR(13),""), CHAR(10),", ")</nowiki>}} replace the return symbols with spaces  in the cell located at {{kbd | key=A1}} <ref>[https://www.ablebits.com/office-addins-blog/2013/12/03/remove-carriage-returns-excel/ 3 ways to remove carriage returns in Excel: formulas, VBA macro, find&replace dialog] {{access | date = 2018-05-24}}</ref><ref>[https://en.wikipedia.org/wiki/ASCII ASCII - Wikipedia]</ref>.

函數說明
* {{kbd | key=CONCAT(CHAR(13), CHAR(10))}} means "CRLF"({{kbd | key=<nowiki>\r\n</nowiki>}}) Windows 標準換行符號
* {{kbd | key=CHAR(13)}} means "Carriage return"(CR, {{kbd | key=<nowiki>\r</nowiki>}}) 舊版 Mac 換行符號
* {{kbd | key=CHAR(10)}} means "Line feed" (LF, {{kbd | key=<nowiki>\n</nowiki>}}) Unix/Linux 換行符號

For Google Sheet
* {{kbd | key=<nowiki>=REGEXREPLACE(A1, "[\r\n]+", " ")</nowiki>}} replaces return symbols with spaces in cell {{kbd | key=A1}} in Google Sheets

函數說明
* {{kbd | key=<nowiki>[\r\n]</nowiki>}} 符合任意類型的換行符號
* {{kbd | key=<nowiki>[\r\n]+</nowiki>}} 符合任意類型的換行符號，出現一次或連續出現

=== Python 如何取代換行符號 ===
* [https://stackoverflow.com/questions/275018/how-can-i-remove-a-trailing-newline-in-python How can I remove a trailing newline in Python? - Stack Overflow] {{access | date = 2019-06-14}}

== Related articles ==
* [https://en.wikipedia.org/wiki/Carriage_return Carriage return - Wikipedia]
* [https://en.wikipedia.org/wiki/Newline Newline - Wikipedia]
* [https://zh.wikipedia.org/zh-tw/%E6%8F%9B%E8%A1%8C 換行 - 维基百科，自由的百科全书]
* [https://zh.wikipedia.org/wiki/%E5%9B%9E%E8%BB%8A%E9%8D%B5 回車鍵 - 維基百科，自由的百科全書]
* [http://violin-tao.blogspot.tw/2016/05/crlflf-bug.html 陳雲濤的部落格: 筆記 CRLF跟LF之區別 --- 隱形的 bug]:「CRLF才是真正的打字機運作方式，你可以想像：打字機打到最右邊，要先return到最左邊之後，再往下一行，所以是CRLF ... ...」
* [https://confluence.qps.nl/fledermaus/questions-answers/other/differences-in-end-of-line-characters-mac-windows-and-linux Differences in end of line characters Mac, Windows, and Linux]
* [https://stackoverflow.com/questions/3059091/how-to-remove-carriage-returns-from-output-of-string php - How to remove carriage returns from output of string? - Stack Overflow]
* Url encoding of {{kbd | key=<nowiki>\r\n</nowiki>}} is {{kbd | key=<nowiki>%0D%0A</nowiki>}}. More details on [https://www.w3schools.com/tags/ref_urlencode.asp HTML URL Encoding Reference]

== References ==

<references />

[[Category: Programming]] 
[[Category: Data Science]] 
[[Category: String manipulation]]
[[Category: Revised with LLMs]]