Sed incremental arithmetic

Question

I want to change a number at the end of a string by incrementing that number by one each time I run a specific sed line.

The string looks like this:

server-port=25555

I was thinking I could run something like this sed line to do it, but it doesn't work.

sed -i 's/port=[0-9]{5}/int(&+1)/'

checkout http://unix.stackexchange.com/questions/36949/addition-with-sed — Vikyboss, Apr 13 '16 at 19:07
you tagged ubuntu, which may have gnu sed, in which case you can use this: http://unix.stackexchange.com/q/231596/117549 -- otherwise, "standard" sed doesn't have math functions built-in. Most people turn to perl for this (see: http://unix.stackexchange.com/q/116372/117549) — Jeff Schaller, Apr 13 '16 at 20:32
If any of the existing answers solves your problem, please consider accepting it via the checkmark. Thank you! — Jeff Schaller, Apr 23 '17 at 12:55

Guido · Answer 1 · 2016-04-13T19:16:33.717

9

I would suggest perl instead of sed for this task:

perl -i -pe 's/(port=)(\d+)$/$1.($2+1)/e' filename

edited Apr 13 '16 at 19:16

answered Apr 13 '16 at 19:09

Guido

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score 1 · Answer 2 · answered Jan 29 '20 at 10:26

1

echo "server-port=25555" | sed  -E 's/(.*-port=)([0-9]+)/echo "\1$((\2+1))"/e'

answered Jan 29 '20 at 10:26

Walter A

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score 0 · Answer 3 · answered Apr 13 '16 at 20:37

If you don't mind a multi-liner, you can work around it using sed and shell math with:

# or however else you're getting the server-port section
num=$(echo server-port=25555 | sed 's/server-port=//') 
v=$((v+1))
sed -i "s/server-port=25555/server-port=$v/" your-file-here

Note the double-quotes around the sed expression; that's so that $v can be interpreted before sed sees it. In this particular case, you could leave the sed expression unquoted, since there's nothing else in there for the shell to (mis)-interpret.

Sed incremental arithmetic

3 Answers3