command execution in linux

Is it possible to avoid sequential command execution in Linux? For eg: I can enter a command ' echo "hello";ls ' . Th开发者_C百科is command will execute by printing "Hello" and then listing the directory. Is possible to make only one command execute at a time,that is only echo command should work blocking 'ls'.

That's called sequential execution (which is what you want, but want to avoid at the same time?).

It might look like both are occuring at once, but they are occuring sequentially.