$cat shebang.sed
#! /bin/sed -f
s/red/xxx/
s/BLUE/1234/
$./shebang.sed rgb
lower (#1): "xxx green blue"
UPPER (#2): "RED GREEN 1234"
$sed -f shebang.sed rgb
lower (#1): "xxx green blue"
UPPER (#2): "RED GREEN 1234"
I may guess what #! is doing. However, I don't say I know it. what is "#!"?