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sed using variables

 
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# 1  
Old 11-09-2008
Question sed using variables
Hi,

I am able to use sed if I hardcode the find and replace values in a shell script.

This works:
sed -e 's/123v/4567/g' /path/aaa.txt
> /path/aaa.txt.tmp

If I use a variable, I am not able to use sed command. why?

This doesnot work:
i=abc
j=bk${i}

sed -e 's/${i}/${j}/g' /path/aaa.txt
> /path/aaa.txt.tmp

Am I doing any mistake?

Thanks and Regards,
# 2  
Old 11-09-2008
sed with double quotes
- if you replace the single quotes (´) in your sample by double quotes (") ,
then the shell will be able to substitute your variables.

- good luck, and success !
# 3  
Old 11-09-2008
Hi Batao,

Thank you very much. Though I searched the site for previous postings with similar question, my attention never went to double quotes. You mentioned exactly where the problem is, and it got solved.

Thank you very much.

With Regards,
# 4  
Old 11-10-2008
Is there any differences between ' single quote and " double quotes....can u explain it in detail........
# 5  
Old 11-10-2008
Yes there is a difference and this thread precisely exhibits it.

Variables are expanded between double quotes but aren't between single ones.
# 6  
Old 11-10-2008
Quote:
Originally Posted by sivakumar.rj
Is there any differences between ' single quote and " double quotes....can u explain it in detail........
See man bash under the section Quoting
Code:
       Enclosing characters in single quotes preserves the literal value of each character within
       the quotes.  A single quote may not occur between single quotes, even when preceded  by  a
       backslash.

       Enclosing characters in double quotes preserves the literal value of all characters within
       the quotes, with the exception of $, ?, and \.  The characters $ and ? retain  their  spe-
       cial  meaning  within  double quotes.  The backslash retains its special meaning only when
       followed by one of the following characters: $, ?, ", \, or <newline>.  A double quote may
       be  quoted within double quotes by preceding it with a backslash.  When command history is
       being used, the double quote may not be used to quote the history expansion character.

 
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