regex to catch commented lines of a conf file

In order to find this line pm.max_children = 50 inside a conf file and change it to pm.max_children = 5, I am using this:

s/^\(pm.max_children = \).*/\15/

In the case, the line may or not be commented (with ';' or '#'). How can I deal with that in a single regex to work with sed?

If the CONF_FILE has this content:

pm.max_children = 500
;pm.max_children = 500
#pm.max_children = 500

This is what I need to accomplish:

pm.max_children = 5
pm.max_children = 5
pm.max_childr开发者_Python百科en = 5

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sed on my machine doesn't seem to support ?, but you can use * instead:

s/^[#;]*[:space:]*\(pm.max_children = \).*/\15/

This matches 0 or more # or ; characters followed by 0 or more whitespace characters.

If you don't care what precedes your keyword, use this, which is simpler, but matches anything:

s/^.*\(pm.max_children = \).*/\15/