How to replace “n” string with a new line in Unix Bash script

Cannot seem to find an answer to this one online...

I have a string variable (externally sourced) with new lines "n" encoded as strings.

"n"

I want to replace those strings with actual new line carriage returns. The code below can achieve this...

echo $EXT_DESCR | sed 's/\n/n/g'


But when I try to store the result of this into it's own variable, it converts them back to strings

NEW_DESCR=`echo $EXT_DESCR | sed 's/\n/n/g'`


How can this be achieved, or what I'm I doing wrong?

Here's my code I've been testing to try get the right results

EXT_DESCR="This is a textnWith a new line"
echo $EXT_DESCR | sed 's/\n/n/g'

NEW_DESCR=`echo $EXT_DESCR | sed 's/\n/n/g'`
echo ""
echo "$NEW_DESCR"


NEW_DESCR

test=$(echo "testingnthis" | sed 's/\n/n/g') && echo "$test"

$()

$()

4 Answers
4

No need for sed, using parameter expansion:

sed

$ foo='1n2n3'; echo "$foo//'n'/$'n'"
1
2
3


With bash 4.4 or newer, you can use the E operator in $parameter@operator:

bash 4.4

E

$parameter@operator

$ foo='1n2n3'; echo "$foo@E"
1
2
3


Other answers contain alternative solutions. (I especially like the parameter expansion one.)

Here's what's wrong with your attempt:

In

echo $EXT_DESCR | sed 's/\n/n/g'


the sed command is in single quotes, so sed gets s/\n/n/g as is.

s/\n/n/g

In

NEW_DESCR=`echo $EXT_DESCR | sed 's/\n/n/g'`


the whole command is in backticks, so a round of backslash processing is applied. That leads to sed getting the code s/n/n/g, which does nothing.

s/n/n/g

A possible fix for this code:

NEW_DESCR=`echo $EXT_DESCR | sed 's/\\n/\n/g'`


By doubling up the backslashes, we end up with the right command in sed.

Or (easier):

NEW_DESCR=$(echo $EXT_DESCR | sed 's/\n/n/g')


Instead of backticks use $( ), which has less esoteric escaping rules.

$( )

Note: Don't use ALL_UPPERCASE for your shell variables. UPPERCASE is (informally) reserved for system variables such as HOME and special built-in variables such as IFS or RANDOM.

ALL_UPPERCASE

UPPERCASE

HOME

IFS

RANDOM

This printf would do the job by interpreting all escaped constructs:

printf

printf -v NEW_DESCR "%b" "$EXT_DESCR"


-v option will store output in a variable so no need to use command substitution here.

-v

Problem with your approach is use of old back-ticks. You could do:

NEW_DESCR=$(echo "$EXT_DESCR" | sed 's/\n/n/g')


Assuming you're using gnu sed as BSD sed won't work with this approach.

gnu sed

BSD sed

%b

Depending on what exactly you need it for:

echo -e $EXT_DESCR


might be all you need.

From echo man page:

-e
enable interpretation of backslash escapes

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