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I am doing a update on the file test.txt which stores some info about storybooks

I've the code below for the function but i realise that using this method of grep, i am unable to get the rest of the values for price quantity and sold which are not mentioned in the grep command.

Is there a better command i can use for this case?

Thanks in advance for replies. :)

echo "Title: "
read title
echo ""
echo "Author: "
read author
echo ""
echo "Number of copies sold: "
read numSold

if grep -iq "$title:$author:" test.txt
then
echo "Current Book Info :"
echo "$title, $author, $price, $quantity, $sold"
echo ""

newQuantity=`expr $quantity - $numSold`
newSold=`expr $sold + $numSold`
sed -i "s/^\($title:$author:[^:]*\):[^:]*:/\1:$newQuantity:/" BookDB.txt 
sed -i "s/^\($title:$author:.*\):.*$/\1:$newSold/" BookDB.txt 


echo "New Book Info :"
echo "$title, $author, $price, $quantity, $sold"
fi
user3245403
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  • 3rd reminder: This is tailor made job of awk – anubhava Jan 28 '14 at 18:54
  • You are using a text file as if it were a database. I'm not saying it is impossible, but it is clumsy and (for big datasets) slow. Please consider using a simple database engine, e.g. SQLite. – Ruud Helderman Jan 28 '14 at 19:09

1 Answers1

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Well unfortunately the build of the test.txt is unknow. If you could show an example that can help.

But if the Price quantity and other staff are in the 1-2 line away from the line you grepping you can use the grep -A 2 (which will grep 2 next lines) or -B 2 (2 lines from above) after that u can just remove the '\n'from the results and print it :

grep -A 2 "$title:$author:*" | tr '\n' ' '

this will give you a line (build out of 3 lines) with all the data. Of course its based on the how test.txt is build.

some thing like this : 

> grep -A 2 "Konan Doil:Story" test.txt
Konan Doil:Story
Price - $$$$$
Quantity - XXXX, Sold - 99999

In response to the comment below : I think its better then use array to save the input. after that u can do with array what ever you want as the values are same (Index 0 = Author, 1 = Book Name ... etc.)

 >IFS=$':'; i=0 ; for line in $(grep "Konan Doil:Good" test.txt) ; do arr[$i]=$line; i=$(($i + 1)) ; done
 >echo "${arr[0]}"
Konan Doil
>echo "${arr[1]}"
Good story
 >echo "${arr[3]}"
XXXXX
 >echo "${arr[4]}"
YYYYYY
 >echo "${arr[2]}"
$$$$$
 >
Artem
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