Using sed with back-references calculated-CodePudding

I would like

pm.max_children = 5

to become;

pm.max_children = 8

and have been working on it and got no soludtions. Backreferences like \1 or \2 don't seem to be working with calculation.

sed -i -E "s/(pm.max_children)[^=]*=\s*(. )/\1 = $(echo \2 3)/" /usr/local/etc/php-fpm.d/www.conf

Using perl commands are OK as well as long as it is solved.

Thank you.

CodePudding user response：

perl -i.bak -wpe's/pm.max_children\s*=\s*\K([0-9] )/$1   3/e' file

This keeps a backup due to .bak; remove that (after testing) if you don't need a backup.

The \K drops all previous matches so they are not consumed and don't have to be restored in the replacement part.

CodePudding user response：

There are many ways, this is one of them:

perl -lpe 's/(?<= = )(\d)/${1} 3/e' <<< 'pm.max_children = 5'

for exact match:

perl -lpe 's/pm.max_children = \K(\d)/${1} 3/e' <<< 'pm.max_children = 5'

just match a number at the end:

perl -lpe 's/(\d)$/${1} 3/e' <<< 'pm.max_children = 5'

output:

pm.max_children = 8

For files, you can use -i in-place saving and instead of <<< (here document which is for testing) use a file.

perl -i -lpe '...' <FILE>

CodePudding user response：

Using sed

$ sed 's/\(.* \)\(.*\)/echo \1 \$((\2 3))/e' /usr/local/etc/php-fpm.d/www.conf
pm.max_children = 8