Trying to do a simple sed substitution but I'm confused about what needs to be escaped

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I have this string: '$'nwnwnwnnn

And want to change it to: { bitset<9>(0bnwnwnwnnn), '$'},

I've looked at many similar questions for different shells using their methods but nothing has worked. I'm generally in zsh but I can use bash or another shell.

The general form I've been trying is this:

sed -E -i new s/(\'.\')([nw]+)/{ bitset<9>(0b\2), \1},/g thing.txt

It should work for any character other than $ and any sequence of n or w.

I'm generally confused as to what I need to escape here. Some answers on this site said to escape the parenthesis in the first part of the substitution.

Am I using -i incorrectly?

sed shell regex
1 Answers

You need to escape the parentheses to create a capture group if you're using basic regexp, you don't escape them if you're using extended regexp. The -E option to GNU sed, and the -r option to standard sed, enable extended regexp, so you don't need to escape them.

If you only want to match $ rather than allow any character in the quotes, you need an escaped $.

You need to put the entire s/// command inside quotes, as it must be a single argument to the sed command.

When using -i, it's conventional to put a . before the suffix. Also, the suffix is put on the saved copy of the original file, not the new file that you're creating with the changes, so new is a poor suffix.

sed -E -i .bak "s/('\$')([nw]+)/{ bitset<9>(0b\2), \1},/g" thing.txt
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