How to increment a number in several files if the number is not always the same ?

Question

Hi,

I have several files containing this line

Release: X

I want to increment X in all the files.

If X was constant between the files, I could have a bash script looping around the files and doing ($1 containing the former release number and $2 the new one, ie. $1 + 1) :

sed 's/Release: '$1'/Release: '$2'/' <$file >$file.new

Now, how should I do if the release number is different between files ?

Is it doable with sed ?

should I use another tool ?

Answer 1

Use awk - it's exactly the right tool for this:

awk '/Release: [0-9]+/ { printf "Release: %d\n", $2+1 }' < $file > $file.new

Translation:

• Search for lines that contain "Release: " followed by one or more digits.
• Print "Release: " followed by a number and a newline. The number is the second word in the input line (the digits), plus 1.

Answer 2

This perl one-liner will do the same as the awk script, but not destroy the rest of the file or the rest of the lines that contain the release.

 perl -pe "$_=~s/Release: (\d+)/'Release: '. ($1+1)/e;" < file > file.new