I have installed ClamAV to scan for viruses. It has 2 commands for scanning: these are clamscan and clamdscan. I use clamdscan because it is faster.
However, clamdscan cannot scan within home directories, or any directory it does not have permissions for, even when running as root. clamscan does not have this problem.
Judging by the first line, this script is a set of Bash commands.
If this line is there, when the script is executed it will run as a Bash script.
This line is required for it to work as a Bash script; if it isn't there, it will execute using the kernel, and it won't work because it's not a binary program.
If you want it all in one line, just copy and paste it into a terminal that already runs Bash, and exclude the first line. But why do you want it in one line in the first place? Multiline scripts have no performance drop, and they are more readable.