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- - Bash - Replace a text with a variable containing new lines character (https://www.linuxquestions.org/questions/programming-9/bash-replace-a-text-with-a-variable-containing-new-lines-character-4175629468/)

vikas027

05-11-2018 06:04 AM

Bash - Replace a text with a variable containing new lines character

Hey All,

I am trying to replace a variable in sed, usually, it can be done by double quotes but my variable has new lines characters and backslashes which somehow is not working.

This is a sample variable

Code:

# echo $CLIENT_KEY

--BEGIN PRIVATE KEY--\nAAA\nBBB\nCCC\n--END PRIVATE KEY--

#

I want to replace this variable's value in a file

Code:

# cat myfile

ABC

CLIENT_KEY

#



# cat myfile | sed "s/CLIENT_KEY/${CLIENT_KEY}/"  (does not works)

ABC

--BEGIN PRIVATE KEY--\nAAA\nBBB\nCCC\n--END PRIVATE KEY--

#

Thanks!

Turbocapitalist

05-11-2018 06:18 AM

I'm not sure how it can be done with the multiple line replacement. It's easy with Perl 5 however.

Code:

cat myfile | perl -p -e "s|CLIENT_KEY|${CLIENT_KEY}|"

wpeckham

05-11-2018 06:23 AM

#1 this appears to be a SED question, not a BASH question, so your title is misleading.

#2 for what you want to do, I am not sure that SED is the correct tool. PERL would be optimal, GSAR would serve.

Could we have some detail about what you are really trying to achieve, and why you selected SED (not BASH) to approach the problem?

syg00

05-11-2018 07:01 AM

The two character text string "\n" is just that - not a newline unless interpolated somehow. Perl, sed would make no difference.
Embedding 0x0A might work. Untested.

danielbmartin

05-11-2018 07:32 AM

Help us to help you. Start by constructing a simplified InFile such as ...

Code:

--BEGIN PRIVATE KEY--\nAAA\nBBB\nCCC\n\n--END PRIVATE KEY--

... and then construct the desired OutFile. Post both files here.

These files will facilitate understanding and give us an example for testing.

Daniel B. Martin

.

vikas027

05-11-2018 08:16 AM

Quote:

Originally Posted by Turbocapitalist (Post 5853207)

I'm not sure how it can be done with the multiple line replacement. It's easy with Perl 5 however.

Code:

cat myfile | perl -p -e "s|CLIENT_KEY|${CLIENT_KEY}|"

Hey,

Thanks, but this did not work, it interpolates "\n" into new lines. I've tried with perl v5.16.3

vikas027

05-11-2018 08:19 AM

Quote:

Originally Posted by wpeckham (Post 5853210)

Hey wpeckham,

I deliberately chose bash and not sed, as I am on bash shell and (as you correctly hinted) that sed may not be the correct tool. I have tried sed, because that was the first tool which came into my mind for replacing text and which has been working great for all my needs so far.

danielbmartin

05-11-2018 08:59 AM

With this InFile ...

Code:

ABC

CLIENT_KEY

DEF

... this code ...

Code:

str="--BEGIN PRIVATE KEY--\nAAA\nBBB\nCCC\n\n--END PRIVATE KEY--"

sed "s/CLIENT_KEY/$str/"<$InFile >$OutFile

echo "InFile ...";  cat $InFile;  echo "End Of InFile ($(wc -l <$InFile) lines)."

echo

echo "OutFile ..."; cat $OutFile; echo "End Of OutFile ($(wc -l <$OutFile) lines)."

... produced this result ...

Code:

InFile ...

ABC

CLIENT_KEY

DEF

End Of InFile (3 lines).



OutFile ...

ABC

--BEGIN PRIVATE KEY--

AAA

BBB

CCC



--END PRIVATE KEY--

DEF

End Of OutFile (8 lines).

Daniel B. Martin

.

Turbocapitalist

05-11-2018 09:10 AM

Quote:

Originally Posted by vikas027 (Post 5853252)

... it interpolates "\n" into new lines. I've tried with perl v5.16.3

That's what you asked for above. If not please show the files as danielbmartin requested above so that we can see what you are trying to achieve.

danielbmartin

05-11-2018 09:20 AM

... Or maybe this is what you want ...

With this InFile ...

Code:

ABC

CLIENT_KEY

DEF

... this code ...

Code:

str="--BEGIN PRIVATE KEY--\nAAA\nBBB\nCCC\n\n--END PRIVATE KEY--"

sed "s/CLIENT_KEY/$str/"<$InFile  \

|paste -s -d~ -                    \

|sed 's/~/\\n/g'                  \

>$OutFile

echo "InFile ...";  cat $InFile;  echo "End Of InFile ($(wc -l <$InFile) lines)."

echo

echo "OutFile ..."; cat $OutFile; echo "End Of OutFile ($(wc -l <$OutFile) lines)."

... produced this OutFile ...

Code:

ABC\n--BEGIN PRIVATE KEY--\nAAA\nBBB\nCCC\n\n--END PRIVATE KEY--\nDEF

Daniel B. Martin

.

MadeInGermany

05-12-2018 03:22 AM

I think the two characters \ and n should be kept here. But a RE interprets it.
How about bash (as the title already suggests)?

Code:

str="--BEGIN PRIVATE KEY--\nAAA\nBBB\nCCC\n\n--END PRIVATE KEY--"

while IFS= read -r line

do

  case $line in

  (CLIENT_KEY*) line=$str;;

  esac

  printf "%s\n" "$line"

done <myfile

wpeckham

05-12-2018 06:45 AM

To prevent things like slash codes from being interpreted by the shell/command line and programs you would use single quotes instead of doble quotes. Somehow I doubt if that is really what you want. Normally a key file will contain embedded newlines at those locations. Why does the interpretation of the newline concern you?

vikas027

05-12-2018 08:25 AM

Quote:

Originally Posted by MadeInGermany (Post 5853559)

I think the two characters \ and n should be kept here. But a RE interprets it.
How about bash (as the title already suggests)?

Code:

str="--BEGIN PRIVATE KEY--\nAAA\nBBB\nCCC\n\n--END PRIVATE KEY--"

while IFS= read -r line

do

  case $line in

  (CLIENT_KEY*) line=$str;;

  esac

  printf "%s\n" "$line"

done <myfile

Excellent, this solves my problem. Thanks much MadeInGermany.

Thanks everyone for your time.

MadeInGermany

05-12-2018 05:19 PM

Quote:

Originally Posted by wpeckham (Post 5853617)

To prevent things like slash codes from being interpreted by the shell/command line and programs you would use single quotes instead of doble quotes...

You mean

Code:

str='...'

Agreed.
Indeed within " " the shell does special treatment of $ and " and ` characters (and allows \ escape of them, therefore the \ character is a bit special, too).
BTW once stored in a variable, the shell does not do further special treatment of "$str"

vikas027

05-30-2018 08:47 PM

I have also found a neat python solution for the same

Code:

f = open(file, 'r')

print f.read().replace('\n', '\\n')[:-1]

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