How to remove carriage return characters from text in Linux

When the carriage return character ( Ctrl+M ) makes you nervous, don't worry. There are several simple ways to eliminate them.

The "carriage return" character goes back a long way -- to the time when typewriters had a mechanism or lever that moved the frame that held the paper rollers to the right so that letters could be entered again on the left. They kept it for text files on Windows, but never on Linux systems. This incompatibility can sometimes cause problems when you try to work on Linux with files created on Windows, but it's a very easy problem to fix.

If you use od ( Octal dump octal dump ) command, the carriage return (also represented by Ctrl+M ) character will be displayed as octal 15. The characters CRLF are commonly used to represent the carriage return and line feed sequence that ends a line in Windows text files. Those who pay attention to the octal dump will see \r\n . In contrast, Linux text ends only with a newline character.

Here is an example of od output, with CRLF characters in the line highlighted, along with their octal equivalents.

$ od -bc testfile.txt
0000000 124 150 151 163 040 151 163 040 141 040 164 145 163 164 040 146
  T hisisatestf
0000020 151 154 145 040 146 162 157 155 040 127 151 156 144 157 167 163
  ilefrom Windows
0000040 056 015 012 111 164 047 163 040 144 151 146 146 145 162 145 156 <==
  . \r \n I t ' s different <==
0000060 164 040 164 150 141 156 040 141 040 125 156 151 170 040 164 145
  tthana U nixte
0000100 170 164 040 146 151 154 145 015 012 167 157 165 154 144 040 142 <==
  xtfile \r \nwouldb <==

While these characters are not a big problem, they can sometimes be disruptive when you want to parse the text in some way and don't want to encode their presence.

3 Ways to Remove Carriage Returns from Text

Fortunately, there are several ways to easily remove the carriage return character. There are three options:

dos2unix

You may have trouble installing it, but dos2unix is ​​probably the easiest way to convert Windows text to Unix/Linux text. A command takes one parameter. No second file name is needed. The file will be modified directly.

$ dos2unix testfile.txt
dos2unix: converting file testfile.txt to Unix format...

You should find that the file length decreases, depending on the number of lines it contains. A file containing 100 lines may be reduced by 99 characters because only the last line does not end with a CRLF character.

Before:

-rw-rw-r-- 1 shs shs 121 Sep 14 19:11 testfile.txt

after:

-rw-rw-r-- 1 shs shs 118 Sep 14 19:12 testfile.txt

If you need to convert a lot of files, don't repair them one at a time. Instead, put them all in one directory and run a command like:

$ find . -type f -exec dos2unix {} \;

In this command, we use find to locate regular files and then run the dos2unix command to convert them one at a time. {} in the command will be replaced by the file name. When running, you should be in the directory containing the file. This command may damage other types of files, such as files that contain octal 15 in contexts other than text files (eg bytes in an image file).

sed

You can also use the stream editor sed to remove the carriage returns. However, you must provide a second file name. Here are some examples:

$ sed -e “s/^M//” before.txt > after.txt

One very important thing to note is that you should not type the characters you see. You must press Ctrl+V followed by Ctrl+M to enter ^M . s is the substitute command. The slash separates the text we want to find ( Ctrl + M ) and the text we want to replace it with (here, nothing).

vi

You can even use vi to remove the carriage returns ( Ctrl+M ), but this assumes you don't have hundreds of files open and are perhaps making some other modifications. You can type : to enter the command line, then enter the following string. As with sed , ^M in the command needs to be ^ via Ctrl+V , and then Ctrl+M to insert M %s is the replacement operation, and the slash again separates the character we want to delete and the text (nothing) we want to replace it with. g (global) means execute on all lines.

:%s/^M//g

Summarize

The dos2unix command is probably the easiest to remember and most reliable way to remove carriage returns from text. The other options are a little more difficult to use, but they offer the same basic functionality.

via: https://www.networkworld.com/article/3438857/how-to-remove-carriage-returns-from-text-files-on-linux.html

Summarize

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