Do mathematical operation on every line of a given file for the first value found to be replaced (other lines stay untouched)

n=1000;f="test.csv";r='([0-9]+.{0,1}[0-9]*)';echo -n "" > new_${f};cat $f | while read l;do val=`echo $l | egrep -o $r` ; if [ ! -z $val ];then newval=`echo $val \* $n | bc -l`;l=`echo $l | sed "s/$val/$newval/"`;fi;echo $l >> new_${f};unset val;done
The given file may contain any kind of characters. This is compatible for most simple mathematical operation. For the first number found, it will be replaced by the result of a factor operation of 1000. To change the filename or multiplactor or number regular expression, change the first fixed values.
Sample Output
For a given filename such as test.csv, a new filename new_test.csv will be created containing the new values after the math operation.
command source: cat test.csv
command output: cat new_test.csv

0
By: s333
2017-04-26 18:04:07

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What do you think?

Any thoughts on this command? Does it work on your machine? Can you do the same thing with only 14 characters?

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