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| Carriage return characters (CRs) are used in line ending markers on some systems. There are three different kinds of line endings in common use: | |
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| All these are from the [http://www.student.northpark.edu/pemente/sed/sed1line.txt sed one-liners page]: | *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: |
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| 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$//' dosfile # GNUism - does not work with Unix sed! |
cat -e yourscript |
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| If you want to remove all CRs regardless of whether they are at the end of a line, you can use {{{tr}}}: | If you see something like this: {{{ command^M$ ^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: |
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| tr -d '\r' < dosfile | ex -sc $'%s/\r$//e|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: | 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. |
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| ---- Another way to check it: |
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| sed $'s/\r$//' dosfile # BASH only | 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 |
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| Some distributions have a {{{dos2unix}}} command which can do this. In vim, you can use {{{:set fileformat=unix}}} to do it. | 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 }}} |
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:
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