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How to use AWK/SED to insert a line?

Posted on 2008-10-01
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Last Modified: 2013-12-26
I have a file that looks like this:

Mary=Ann
Ann=Mary
Fake=Fake

Joe=John
Doe=Doe



I want to find Fake=Fake and insert another line before it. This change then needs to be written back to the same file. The replacement value is in a variable, say, $__changes

I have been trying sed but for some reason it creates a 0byte file if the source and target files are the same. I am ok if you can provide an awk solution.

__changes='$1.something'

cat 'file1.txt' | sed '
/Fake=FakeX/ i\
$__changes
' > 'file1.txt'

This doesn't work if I try a variable in the replacement text.

Please note I need to insert before only the first instance of the match.

Thanks for your help.
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Question by:infa007
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5 Comments
 
LVL 84

Expert Comment

by:ozo
ID: 22613806
>'file1.txt
opens and clears the output before sed runs
try sed -i
0
 
LVL 84

Expert Comment

by:ozo
ID: 22613869
sed -i.bak -e '/Fake=Fake/ i\
'$__changes'
'  file1.txt
0
 

Author Comment

by:infa007
ID: 22615073
I get an error: sed: Not a recognized flag: i
0
 
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Accepted Solution

by:
gisellla_igr earned 500 total points
ID: 22615298
try this

file=file1.txt
tmpFile=${file}$$
__changes="nueva linea"
cat $file | sed "
/Fake=Fake/ i\\
$__changes
" > $tmpFile
mv $tmpFile $file

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0
 

Author Closing Comment

by:infa007
ID: 31501945
Thanks, exactly what I wanted!
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