Add one line of code after a specific matched line-CodePudding

I have a file like this:

some
code
const parameterParens = new WeakSet();
some
other 
code

I want to turn it into:

some
code
const parameterParens = new WeakSet();
module.exports.create.offsets = offsets;
some
other 
code

What I am doing at the moment is intolerable:

sed -i -- 's/const parameterParens = new WeakSet();/const parameterParens = new WeakSet();\nmodule.exports.create.offsets = offsets;\n/g' file.js

I would like to at least not have to repeat the match line:

sed -i -- 's/(const parameterParens = new WeakSet\(\);)/$1\nmodule.exports.create.offsets = offsets;\n/g' file.js

Which doesn't work. I am not set on using sed, but I would like to keep it as basic as possible (no perl, etc).

CodePudding user response：

If you use awk instead of sed then you don't have to worry about regexp or backreference metachars like you would with sed (see is-it-possible-to-escape-regex-metacharacters-reliably-with-sed) since awk has literal string operations:

$ awk '{print} $0=="const parameterParens = new WeakSet();"{ print "module.exports.create.offsets = offsets;" }' file
some
code
const parameterParens = new WeakSet();
module.exports.create.offsets = offsets;
some
other
code

CodePudding user response：

Using sed

$ sed 's/new WeakSet();/&\nmodule.exports.create.offsets = offsets;/' input_file
some
code
const parameterParens = new WeakSet();
module.exports.create.offsets = offsets;
some
other
code