How do I convert a file from DOS format to UNIX format (remove CRs from CR-LF line terminators)?
Carriage return characters (CRs) are used in line ending markers on some systems. There are three different kinds of line endings in common use:
- Unix systems use Line Feeds (LFs) only.
- MS-DOS and Windows systems use CR-LF pairs.
- Old Macintosh systems use CRs only.
If you're running a script on a Unix system, the line endings need to be Unix ones (LFs only), or you will have problems. You can check the kind of line endings in use by running:
cat -e yourscript
If you see something like this:
command^M$ ^M$ another command^M$
then you need to remove the CRs. There are a plethora of ways to do this.
To remove them from a file, ex is a good standard way to do it:
ex -sc $'%s/\r$//e|x' file
There are many more ways:
Some systems have a dos2unix command which can do this. Or recode, or fromdos.
You can also use col <input.txt > output.txt
In vim, you can use :set fileformat=unix to do it and save it with a ":w".
- You can use Perl:
perl -pi -e 's/\r\n/\n/' filename
Another way to check it:
The output tells you whether the ASCII text has some CR, if that's the case. Note: this is only true on GNU/Linux. On other operating systems, the result of file is unpredictable, except that it should contain the word "text" somewhere in the output if the result "kind of looks like a text file of some sort, maybe".
imadev:~$ printf 'DOS\r\nline endings\r\n' > foo imadev:~$ file foo foo: commands text arc3:~$ file foo foo: ASCII text, with CRLF line terminators
And another way to fix it:
nano -w yourscript
Type Ctrl-O and before confirming, type Alt-D (DOS) or Alt-M (Mac) to change the format.
Or, if available, you can use the program dos2unix, sometimes also called tofrodos.