Shell Scripting

Reading a file containing escaped sequences

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Join Date: Mar 2009

Posts: 3

Reputation: lml108 is an unknown quantity at this point

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lml108

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Newbie Poster

Reading a file containing escaped sequences

Mar 23rd, 2009

Hi,
I've a file having some regular expressions.
e.g. cat regex.txt
[\t\n]
abc.*pqr

If I write a small bash script as below,

while read line
do
echo -E "$line"
done < regex.txt

even with -E switch passed to echo the output is
[tn]
abc.*pqr

So the backslashes have vanished in the first regular expression.
Is there a way to retain all backslashed escape sequences
while reading a file using the while loop ?

Thanks,
Mahendra

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Join Date: Feb 2007

Posts: 54

Reputation: radoulov is an unknown quantity at this point

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radoulov

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Re: Reading a file containing escaped sequences

Mar 23rd, 2009

 Help with Code Tags 
 Shell Scripting Syntax (Toggle Plain Text) 
while IFS= read -r;do 
  printf '%s\n' "$REPLY"
done<regex.txt
while IFS= read -r;do 
  printf '%s\n' "$REPLY"
done<regex.txt

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Join Date: Mar 2009

Posts: 3

Reputation: lml108 is an unknown quantity at this point

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lml108

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Newbie Poster

Re: Reading a file containing escaped sequences

Mar 23rd, 2009

•

Originally Posted by radoulov

Help with Code Tags

Shell Scripting Syntax (Toggle Plain Text)
while IFS= read -r;do 
  printf '%s\n' "$REPLY"
done<regex.txt
while IFS= read -r;do printf '%s\n' "$REPLY" done<regex.txt

Thanks Radoulov. It's now reading \ literally without interpreting it.

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Join Date: Aug 2007

Posts: 165

Reputation: Fest3er is an unknown quantity at this point

Solved Threads: 18

Fest3er

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Junior Poster

Re: Reading a file containing escaped sequences

Mar 23rd, 2009

Why's it work?

Matter inside double quotes (") is interpreted/evaluated by the shell. Matter inside single quotes (') is not.

It's a handy tool, but can cause some stubbed toes along the way.