Sed regex to add multiple spaces

Question

I'm looking for a clean way to add multiple spaces to a sed statement. Having literal spaces in the statement works:

sed -i 's/this is a test/\n          and so is this/' test_file.txt

but I was hoping for a more precise way to accomplish this with regex. Thanks!

What do you mean by more precise? Do you mean that you want to insert an arbitrary number of spaces by using that number? — Stéphane Chazelas, Jul 25 '18 at 13:37
Yes, so instead of 10 literal spaces, specifying the number "10" — GreNIX, Jul 25 '18 at 13:38

Stéphane Chazelas · Accepted Answer · 2018-07-25 13:43:12Z

With bash or zsh, you can get an arbitrary number of spaces in a variable with:

printf -v spc %10s
sed -i "s/this is a test/&\n${spc}and so is this/" test_file.txt

With zsh, you can also do:

sed -i "s/this is a test/&\n${(l:10:)}and so is this/" test_file.txt

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