HowTo: UNIX / Linux Convert DOS Newlines CR-LF to Unix/Linux Format

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How do I convert DOS newlines CR/LF to Unix/Linux format?

To converts text files between DOS and Unix formats you need to use special utility called dos2unix. DOS text files traditionally have carriage return and line feed pairs as their newline characters while Unix text files have the line feed as their newline character.


UNIX/Linux Commands

You can use the following tools:

  • dos2unix (also known as fromdos) – converts text files from the DOS format to the Unix
  • unix2dos (also known as todos) – converts text files from the Unix format to the DOS format.
  • sed – You can use sed command for same purpose
  • tr command
  • Perl one liner

Task: Convert DOS file to UNIX format

Type the following command to convert file called myfile.txt:
$ dos2unix myfile.txt

However above command will not make a backup of original file myfile.txt. To make a backup of original file. The original file is renamed with the original filename and a .bak extension. Type the following command:
$ dos2unix -b myfile.txt

Task: Convert UNIX file to DOS format

Type the following command to convert file called myfile.txt:
$ unix2dos myfile.txt
$ unix2dos -b myfile.txt

Task: Convert Dos TO Unix Using tr Command

Type the following command:

tr -d '\r' < input.file > output.file

Task: Convert Dos TO Unix Using Perl One Liner

Type the following command:

perl -pi -e 's/\r\n/\n/g' input.file

Task: Convert UNIX to DOS format using sed command

Type the following command if you are using bash shell:
$ sed 's/$'"/`echo \\\r`/" input.txt > output.txt
Note: sed version may not work under different UNIX/Linux variant,refer your local sed man page for more info.

Task: Convert DOS newlines (CR/LF) to Unix format using sed command

If you are using BASH shell type the following command (press Ctrl-V then Ctrl-M to get pattern or special symbol)
$ sed 's/^M$//' input.txt > output.txt
Note: sed version may not work under different UNIX/Linux variant, refer your local sed man page for more info.

Posted by: Vivek Gite

The author is the creator of nixCraft and a seasoned sysadmin, DevOps engineer, and a trainer for the Linux operating system/Unix shell scripting. Get the latest tutorials on SysAdmin, Linux/Unix and open source topics via RSS/XML feed or weekly email newsletter.


24 comment

  1. Howto: UNIX or Linux convert DOS newlines CR-LF to Unix/Linux format

    THANK YOU! to who ever wrote this. I’ve been messing around with this for quite a while. This even works on AIX’s legacy version of sed. My day has been so made by this little nugget.

  2. Your UNIX to DOS sed script is incorrect if what you want is CRLF.

    $ echo | sed ‘s/$'”/`echo \\\r`/” | hexdump
    0000000 0a0d

    ASCII 0/13 is decimal 013, hex 0d, octal 015, bits 00001101: called ^M, CR
    Official name: Carriage Return

    ASCII 0/10 is decimal 010, hex 0a, octal 012, bits 00001010: called ^J, LF, NL
    Official name: Line Feed

    For CRLF you want 0d0a. Your producing LFCR here.

  3. Dear John,

    Actually, the scripts are correct. Hexdump is reversing the byte order (integer format)

    Try this for example and as a simplified script:

    $ echo TEST | sed ‘s/$/\r/’ | hexdump -C

    Then try it without the -C.
    You will notice that the 54’s (T) are next to each other. (ETTS)

  4. Impressive i would say.. I used dos2unix on CentOS 5.3 without any problems and a file of 300,000 got modified in less then 15 secs… compared it to using notepad++ on windows and your computer would freeze up for at least 2 mins for the same file ;).

  5. sed ‘s/$'”/`echo \\\r`/” input.txt > output.txt
    leaves one extra CR at the end of the file.
    This makes the suggestion broken.

  6. Do we have dos2unix equivalent command on Window OS. Ie. A Window command to convert dos newlines to unix format.

    Thanks for your help.

  7. Thanks!
    I was just about to write a shellscript for this, but then I just googled it because I forgot if it was /n to /r or how :P It works!!!

    Side note:
    For people with problems about duplicates moved from Windows to Linux on Garry’s Mod servers they should use “dos2unix STEAM*/*.txt” to avoid trying to convert directories. There’s a lot of trouble with user created directories otherwise. The program tries to convert directories – which is a bit annoying.

  8. I found the sed unix to dos to not work, it ended up leaving CRs at the end of lines and CRLF at the start of every line….

    instead the following correctly left CRLFs at the end of every line (that originally had LFs)

    sed “s/$/`echo`/” on Ubuntu BASH

  9. For me, `tr -d ‘\r’ output.file` deletes all the carriage returns without replacing them with newlines. `tr ‘\r’ ‘\n’ output.file` works nicely, though

  10. You might also suggest
    sed ‘s/$/\r/’
    This works fine on Cygwin sed, though perhaps not for that pesky last line.

    Thanks for the suggestions.

  11. Excellent article, my favorite method are with tr -d ‘\r’ or simply with vi you do
    :s/^M//g , why I like those is because there are realy simple to remember and work on all environment, unix, linux, aix , solaris etc…

    I try the sugestion of cee , :ff=unix , it’s very cool , the only problem it’s seems it only work on vim , not in vi . Where I work there is no vim , snif , snif.

  12. I found a very easy way… Open file with nano
    # nano file.txt
    press Ctrl+O to save, but before pressing Enter press:
    Alt+D to toggle betwen DOS and Unix/Linux line-endings, or:
    Alt+M to toggle betwen Mac and Unix/Linux line-endings
    then press Enter to save and Ctrl+X to quit.

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