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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:

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:

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:

Another way to check it:

file yourscript

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.

And another way to fix it:

dos2unix filename

2012-07-01 04:05