Need help.. I want to replace a line in a file with a variable

Posted on 2004-10-08
Last Modified: 2010-04-21

Here is what I have...

the file:


the value of the variable is actually the modified Targetline:

echo $rplc

So I have been trying to find a sed line or awk that would assist me. I want to search the file based on the second field (":" delimited btw). The second field will not be changing and should be unique throughout the file.

I am using bash,awk,and sed.
Please help.

Thank in advance!!
Question by:g8ballz0fyre
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Author Comment

ID: 12265142
One more thing about that second field...

There may be instances of the second field where it will read "Electric" and the next line will have "Electric Heat".

Just sat back and realized that if I search on "Electric" it may return more than one line......hmmm more brain cell burning.. need coffee..
LVL 44

Expert Comment

by:Karl Heinz Kremer
ID: 12265729
Try this:



search=`echo $rlpc | awk -F: ' { print $2 } '`
grep :${search}: $file
LVL 44

Expert Comment

by:Karl Heinz Kremer
ID: 12266321
Forgot about the "replace" requirement (which is only mentioned in the subject). Does the replaced line have to be in the same location as the original line was, or is it sufficient to place the new information at the end of the file?
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Author Comment

ID: 12267383
The replacement doesn't neccesarily need to be in the same place...
It looks like this will grab the target line correctly.. so once I have it, how can I delete it?

Then all I would have to do is echo $rplc >> $file.

Sorry about the replacement statement only being in the subject.
LVL 84

Expert Comment

ID: 12267439
grep -v :`echo $rplc | awk -F: ' { print $2 } '`: file > file.$$
mv file.$$ > file

Author Comment

ID: 12267497

Thanks so much for your advice khkremer and ozo, it all is beginning to work.

Do you have any suggestions for like instance of the second field??

There may be instances where the second field will be Admin and Super Admin.
As is sits now running:

search=`echo $rlpc | awk -F: ' { print $2 } '`
grep -v $search > newfile
mv newfile oldfile

It would remove both, Admin and Super Admin, lines from the list...
LVL 44

Accepted Solution

Karl Heinz Kremer earned 250 total points
ID: 12267575
Try this:


rplc="54321:Super Admin:56789:blahblahblah"
search=`echo $rplc | awk -F: ' { print $2 } '`

grep -q ":${search}:" $file
if [ $ret -eq 0 ] ; then
    grep -v ":${search}:" $file  > $file.$$
    echo $rplc  >> $file.$$
    mv -f $file.$$ $file

.. and I'm sorry for the typo in my first script. This script does two grep operations: The first one is to find out if the search string is on the file. If it is, we replace it. If it is not, we are not doing anything.
LVL 84

Expert Comment

ID: 12267611
grep -v :$search: $file > newfile

Author Comment

ID: 12267823
Thanks for the help..both of you!!!

I just put your script as it is and it seems to work flawlessly...

Thanks again!!

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