Did the line after hitting return show up blank or dis you see, >
If you did see that symbol, whatever you entered was not a complete command and it was waiting for more.
However, that command takes a long time to run. It scans the entire hard drive for apps and frameworks.
It runs for a while, then dumps a list of registered plugins, then continues scanning for about a minute or so.
If it didn't finish in five minutes, I would assume something is wrong, but i'm not sure what that would be.
You could run the command with the Verbose option to see what it is doing, but realize you might see lots of lines with errors. Those do not indicate a problem. There just isn't anything that needs to be registered in the file it is referencing.
/System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/LaunchServices.framework/Versions/A/Support/lsregister -v -kill -seed
Again, the error lines are not a problem. Just see where it is hanging up. That may or may not tell us anything, though.