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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"
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4
  • 3
    How are you inspecting NEW_DESCR? Commented Aug 28, 2018 at 19:31
  • 3
    This works for me: test=$(echo "testing\nthis" | sed 's/\\n/\n/g') && echo "$test" consider switch from backticks to $() to capture output to a variable. Commented Aug 28, 2018 at 19:33
  • The comment by @JNevill identifies the problem. See also the answer by @Gunstick to Backticks vs braces in Bash. In summary: expressions inside backticks (but not $()) have a level of quoting removed before they are executed. Commented Aug 28, 2018 at 20:10
  • Is this an XY Question for "how do I turn a JSON string into plaintext?" Commented Aug 28, 2018 at 21:23

4 Answers 4

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13

No need for sed, using parameter expansion:

$ foo='1\n2\n3'; echo "${foo//'\n'/$'\n'}"  
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With bash 4.4 or newer, you can use the E operator in ${parameter@operator}:

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

Thank you!! Parameter Expansion was originally what I wanted to do when I started yesterday, but could not wrap my head around it! This is awesome!
8

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.

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2 Comments

This is great info! I was looking for the parameter expansion initially myself!
I'd include mywiki.wooledge.org/BashFAQ/082, especially for the see also :)
5

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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Comments

3

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.

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1 Comment

I didn't know about %b, nice one +1.

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