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Need shell script to append double quotes for each column in a file

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Top Forums Shell Programming and Scripting Need shell script to append double quotes for each column in a file
# 8  
Old 09-24-2017
Hi,
Thanks to reply but sorry, my question was too short.
So, I try to explain my non-understanding.

If infile contain a line like that
Code:
abc|123"|gh-ch"|23.067"

with this command line
Code:
sed 's/"*\([^|"]*\)"*/"\1"/g' infile

sed with g at the end operate 4 times.
so,

time 1 :
Code:
"* = ''
\([^|"]*\) = abc
"* = ''
pattern = "abc"|123"|gh-ch"|23.067"
               ^

sed stop on the | for the second pass

time 2 :
Code:
"* = ''
\([^|"]*\) = ''
"* = ''
pattern = "abc"|123"|gh-ch"|23.067"
               ^

sed stop on the | for the third pass

etc ...
and sed never stop.

It's my understanding.
It's false but I can't figure out how this work.
That's why I ask.

To obtain the same result
my command line is
Code:
sed 's/"*\([^|"]*\)"*\(|*\)/"\1"\2/g' infile

Thanks.
# 9  
Old 09-24-2017
The regex
Code:
"*\([^|"]*\)"*

applied to
Code:
abc|123"|gh-ch"|23.067"

will yield the first parenthesized subexpression to be used by the back reference
Code:
abc
123
gh-ch
23.067

Any existing double quotes will be excluded from the subexpression and thus the back reference. Does this example help you understand:

Code:
sed ' s/"*\([^|"]*\)"*/X\1X/1; p; s/"*\([^|"]*\)"*/X\1X/2; p; s/"*\([^|"]*\)"*/X\1X/3; p; s/"*\([^|"]*\)"*/X\1X/4' file
XabcX|123"|gh-ch"|23.067"
XabcX|X123X|gh-ch"|23.067"
XabcX|X123X|Xgh-chX|23.067"
XabcX|X123X|Xgh-chX|X23.067X

This User Gave Thanks to RudiC For This Post:
ctac_
# 10  
Old 09-24-2017
Many tanks.
I don't know this type of back reference too
Code:
s/"*\([^|"]*\)"*/X\1X/3
                      ^

# 11  
Old 09-24-2017
That's not a back reference, but one on the s command's flags following the replacement. info sed:

Quote:
FLAGS:

'g'__________Apply the replacement to _all_ matches to the REGEXP, not just the first.

'NUMBER' __Only replace the NUMBERth match of the REGEXP.
Last edited by RudiC; 09-24-2017 at 07:48 AM..
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