Difference between filename and . filename in macOS terminal I'm newbie to MacOS. (I'm using mac OS high sierra 10.13.6)
I installed a software. They said to initialize the software by 

. /path/setsas.sh

I give no thought to . and space, so I just ran

path/setsas.sh

It seemed to run, but after that I couldn't execute any command of the software.
I found that I should have ran the command as it were, and after that it was fine.
So what these . and space mean here, and any guess why I couldn't execute any command at first even though file seemed to run?
I know that . sometimes mean current folder, but it doesn't look like it in this case.
. /path/setsas.sh loads the variables and functions from the script into your current shell session.  It's the same as running source /path/setsas.sh.  Running path/setsas.sh on the other hand spawns a new process.  The variables and functions will not be accessible from your current shell.  That's why the commands weren't working for you.