如何使用emacs查找和删除文本文件中的不可见字符 [英] How to find and remove the invisible characters in text file using emacs

问题描述

我有一个名为COPYING的txt文件，它在Windows上编辑。它包含窗口样式eol

  $ file COPYING 
 COPYING：ASCII英文文本，带有CRLF行终止符
  

我尝试使用dos2unix将其转换为unix样式。以下是输出

  $ dos2unix COPYING 
 dos2unix：跳过二进制文件COPYING 
  

我很惊讶，发现dos2unix程序将其报告为二进制文件。然后使用其他编辑器（而不是emacs），我发现该文件包含一个控制字符。我有兴趣使用emacs查找文件中的所有隐形字符。

通过Googling，我发现以下解决方案使用了tr

  tr -cd'\11\12\40-\176'< file_name 
  

如何在emacs中执行相同的操作。我尝试了hexl模式。 hexl模式在单个缓冲区中显示文本及其对应的ascii值，这是非常好的。如何查找ASCII数值不同于11-12,40-176（即标签，空格和可见字符）的字符。我试图为该搜索创建一个正则表达式，但这是相当复杂的。

解决方案

默认情况下，Emacs不会隐藏任何字符。按 Ctrl + 元 + ％或 Esc 然后 Ctrl + ％如果前者对你的手指太硬，或者如果你愿意，或者code> Mx replace-regexp RET 。然后，对于正则表达式，输入

  [^ @  -  ^ H ^ K  -  ^ _ ^？] 
  

但是，在我写的 ^ H 中，键入 Ctrl + Q 然后是 Ctrl + H ，以字面的方式输入control-H您可以按 Ctrl + Q 然后 Ctrl + 空格为 ^ @ ，通常 Ctrl + Q 然后 Backspace 为 ^？。将这个正则表达式的所有出现替换为空字符串。

由于您在Emacs中打开文件，因此您可以在此处更改其行尾。按 Cx RET f （ Ctrl + X 返回 F ），然后输入 us-ascii-unix 作为文件的新的所需编码。

I have a txt file named COPYING which is edited on windows. It contains windows style eol

$ file COPYING 
COPYING: ASCII English text, with CRLF line terminators

I tried to convert it to unix style using the dos2unix. The below is the output

$ dos2unix COPYING 
dos2unix: Skipping binary file COPYING

I was surprised to find that dos2unix program reports it as an binary file. Then using some other editor(not emacs) i found that the file contains a control character. I am interested to find all the invisible characters in the file using emacs.

By Googling i have found the following solution which uses tr

tr -cd '\11\12\40-\176' < file_name

How to do the same in emacs way. I tried the hexl-mode. The hexl-mode shows text and their corresponding ascii values in a single buffer which is great. How to find the characters which has ASCII values other than 11-12, 40-176(i.e tab, space and visible characters). I tried to create a regular expression for that search, but it is quite complicated.

解决方案

Emacs won't hide any character by default. Press Ctrl+Meta+%, or Esc then Ctrl+% if the former is too hard on your fingers, or M-x replace-regexp RET if you prefer. Then, for the regular expression, enter

[^@-^H^K-^_^?]

However, where I wrote ^H, type Ctrl+Q then Ctrl+H, to enter a "control-H" character literally, and similarly for the others. You can press Ctrl+Q then Ctrl+Space for ^@, and usually Ctrl+Q then Backspace for ^?. Replace all occurrences of this regular expression by the empty string.

Since you have the file open in Emacs, you can change its line endings while you're at it. Press C-x RET f (Ctrl+X Return F) and enter us-ascii-unix as the new desired encoding for the file.

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