Using perl for incrementing numbers in text file

Question

I want to batch-process text files from the command line by adding a static offset to all numbers contained in said files using perl.

For example, if the file contained the line: AN_IDENTIFIER_TOKEN = 1, and the offset is 19 then this line should be transformed to AN_IDENTIFIER_TOKEN = 20,

I tried to use perl -pe 's/(\\d+)$/19+$1/e' file1.txt but that did produce the same output as input (no numbers were changed). What is the correct command to pass to perl?

Using ActiveState Perl 5.24.1 on Windows.

Answer 1

It should work, try this:

perl -pe "s/(\d+)/19+$1/eg" file1.txt

Your regex (\\d+)$ matched only digits at the end of a string, so that won't match 1,

If you want to match only " = <digits>," , then use something like this

perl -pe "s/ = (\d+),/' = '.(19+$1).','/eg" file1.txt

Answer 2

If you want to alter numbers at the ends of the lines in the file, and those numbers are always followed by commas, then you can use tnis

S/(\d+)(?=,\s*$)/$1+19/e

It uses a look-ahead to check that the number is followed by a comma, optional white space, and the end of the line