Using the magic number
When a script file starts with #!, the kernel's spawn and exec
services recognize the file name after the #! as the program to
be run. For example, the z/OS UNIX file /u/userid/util1 contains
the following in the start of the file:
#! /u/userid/othershell
The
kernel recognizes the magic number (#!) and runs /u/userid/othershell.