CODEWITHSUNDEEP
bashshellunixsed
Karthik
Karthik

Reputation: 145

Shell: Ignore escape sequences while replacing a pattern

I have searched this topic and saw some examples but somehow it doesnt work for me. i have to replace one line with another in a file in shell script (which contains file path and extension). I am using below command but replace is not working.

line='a|b|c|\\folder\file.txt'
upd_line='a|b|c|\\folder\file.txt|d'
sed -i 's#$line#$upd_line#g' sample.txt

sample.txt content:

HDR|date

a|b|c|\\folder\file.txt

I am expecting second line to be replaced with content of $upd_line but it remains unchanged. Please advise what am i doing wrong. i tried in bash and ksh with no luck.

Upvotes: 1

Views: 450

Answers (3)

Sundeep
Sundeep

Reputation: 23677

perl would be better suited with quote operators

$ cat sample.txt 
HDR|date    
a|b|c|\\folder\file.txt

$ # adding |d to end of line
$ line='a|b|c|\\folder\file.txt'
$ perl -pe "s/$/|d/ if /\Q$line/" sample.txt
HDR|date    
a|b|c|\\folder\file.txt|d

$ # generic search and replace
$ l='a|b|c|\\folder\file.txt' ul='a|b|c|\\folder\file.txt|d' perl -pe 's/\Q$ENV{l}/$ENV{ul}/' sample.txt
HDR|date    
a|b|c|\\folder\file.txt|d

Upvotes: 1

potong
potong

Reputation: 58473

This might work for you (GNU sed & bash):

a='a|b|c|\\folder\file.txt'
b='a|b|c|\folder\file.txt|d'

qs(){ sed <<<$1 's/[][\\.*^$]/\\&/g';}

sed "s/$(qs $a)/$(qs $b)/" file

This creates a function qs which converts the variable strings to the accepted form in the sed regexp and replacement.

N.B. the use of double quotes around the sed command; this allows the shell to interpolate the shell variables and function calls. If GNU readline is used in your choice of terminal, C-M-e will show you the results of the interpolation before the shell runs the sed command (you may need to requote the results before running them for real).

Upvotes: 2

Arjun Mathew Dan
Arjun Mathew Dan

Reputation: 5298

It will be something like this:

line="a|b|c|\\\\\\\folder\\\file.txt"
sed -i "s#$line#&|d#g" sample.txt

Output:

HDR|date

a|b|c|\\folder\file.txt|d

Upvotes: 2

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