CODEWITHSUNDEEP
bashshellvariablesunix
Skytunnel
Skytunnel

Reputation: 1083

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.

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 text\nWith 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"

Upvotes: 7

Views: 15823

Answers (4)

melpomene
melpomene

Reputation: 85767

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.

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.

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.

Upvotes: 8

anubhava
anubhava

Reputation: 784968

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

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

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

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.

Upvotes: 3

PesaThe
PesaThe

Reputation: 7499

No need for sed, using parameter expansion:

$ foo='1\n2\n3'; echo "${foo//'\n'/$'\n'}"  
1
2
3

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

$ foo='1\n2\n3'; echo "${foo@E}"
1
2
3

Upvotes: 11

mirgleich
mirgleich

Reputation: 53

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

Upvotes: 5

Related Questions