macos - sed throws 'bad flag in substitute command'

Question

I want to run a simple command of replacing absolute paths to relative ones inside a CSS file like this:

sed -i 's//fonts/../fonts/' /Users/sergeybasharov/WebstormProjects/snap/compiled/Content/stylesheets/style.css

It throws this

sed: 1: "/Users/sergeybasharov/W ...": bad flag in substitute command: 'b'

What can be wrong in this simple script?

Answer 1

In your command s//fonts/../fonts/ is being taken as the parameter to the -i option (the suffix to use for the backup file), and the filename argument is being treated as the editing commands.

You need to specify to disable the backup file creation:

sed -i '' ...

In your example:

sed -i '' 's//fonts/../fonts/' /Users/sergeybasharov/WebstormProjects/snap/compiled/Content/stylesheets/style.css

Computers are dumb, they don't figure things out by context, so they can't tell that something beginning with s/ is obviously an editing command, not a suffix.