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Revision 11 as of 2012-02-02 14:08:17
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Comment: bugger off sed, we're talking about files here. go find a stream to play with.
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All these are from the [[http://www.student.northpark.edu/pemente/sed/sed1line.txt|sed one-liners page]]:
sed 's/.$//' dosfile # assumes that all lines end with CR/LF
sed 's/^M$//' dosfile # in bash/tcsh, press Ctrl-V then Ctrl-M
sed 's/\x0D$//' dosfile # GNUism - does not work with Unix sed!

If you want to remove all CRs regardless of whether they are at the end of a line, you can use {{{tr}}}:
To remove them from a file, `ex` is a good standard way to do it:
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tr -d '\r' < dosfile ex -sc $'%s/\r//ge|x' file
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If you want to use the second {{{sed}}} example above, but without embedding a literal CR into your script:

sed $'s/\r$//' dosfile # BASH only

All of the previous examples write the modified file to standard output. Redirect the output to a new file, and then {{{mv}}} it over top of the original.

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:

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//ge|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
    This has the advantage of overwriting the original file, so you don't have to mess with temporary files.

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

BashFAQ/052 (last edited 2022-01-30 01:59:53 by larryv)