Question

I need to replace a value that matches a string=value
so this is what I’ve came up with:

echo "some string=oldvalue" | sed 's/\(some string\=\)(.*)/\1newvalue/'

It works fine, I just wonder if there’s a better, shorter way to accomplish the same

TIA

Answer 1

If some_string is a constant value, just use:

sed 's/some string=.*/some string=newvalue/'

as per the following transcript:

pax> echo "some string=oldvalue" | sed 's/some string=.*/some string=newvalue/'
some string=newvalue

But you may want to consider using a start marker so that you don’t pick up other keys:

sed 's/^some string=.*/some string=newvalue/'

If you wanted to preserve the rest of the line (say, after a space), use:

pax> echo "string=old # comment" | sed 's/string=[^ ]*/string=newvalue/'
string=newvalue # comment

This works by limiting the item after the = to non-space characters.