tr command \n

Sefyir · 04-01-2016, 10:24 PM

I have a file and I'm trying to replace the contents from actual newlines to "interpreted" newlines. How do you escape something that is already meant to be escaped?

Eg.

Code:

hello
goodbye

to

Code:

hello\ngoodbye\n

Some stuff I've tried:

Code:

$ cat file | sed 's:\n:\\\n:g'
hello
goodbye

$ cat file | sed 's:\n:\n:g'
hello
goodbye

$ cat file | tr '\n' \\\n
hello
goodbye

$ cat file | tr '\n' \\\\n
hello\goodbye\\$ cat file | tr '\n' \\\\\n
hello\goodbye\\$ cat file | tr '\n' \\\\\\n 
hello\goodbye\\$ 
$

syg00 · 04-01-2016, 10:54 PM

You can't change what ain't there - record oriented reads give you the record; up to the newline.
You need to be able to read the entire file as a single record so the newlines are still embedded. perl does it, awk can be fudged to do it, and you can use sed to read each record and append a newline before the next record is appended; the change them all to something else.

Use whichever you feel most comfortable with.

Sefyir · 04-01-2016, 11:28 PM

I guess I don't fully understand. I was unable to get sed to work by itself (most searches were for creating actual newlines and not the characters \n)

After a lot of trial and error, this seems to work.

Code:

cat file | tr \\n \# | sed 's:#:\\n:g'
hello\ngoodbye\n\n

Hopefully there won't be any #'s in the file ever! (I don't expect there to be)

syg00 · 04-01-2016, 11:32 PM

Yes I was also going to suggest something similar. I've used "\v" (rather than #) in the past; not likely to be many of them in normal text.

pan64 · 04-02-2016, 01:50 AM

Quote:

Originally Posted by Sefyir

I guess I don't fully understand. I was unable to get sed to work by itself

Just to explain a bit better: sed uses \n as line separator, that is not part of the text processed therefore you cannot replace it by that way.
tr itself replaces only chars to chars, so you cannot replace a single char (\n) to a longer string.

rknichols · 04-02-2016, 09:34 AM

You can do it with sed, but you have to tell it to join all the lines into a single string. That string will have embedded newline characters, which you can then replace with whatever you choose.

Code:

sed -n 'H;${x;s/^\n//;s/\n/\\n/g;p}'