#!/bin/sh

Shell Programming and Scripting
1

Why #!/bin/sh (the very first line of the script) is not treated as comment. Though it starts with #, which is meant for comment.

2

Hi, see /t/the-whole-story-on-usr-bin-ksh/170227/1

3

"The sha-bang (#!) at the head of a script tells your system that this file is a set of commands to be fed to the command interpreter indicated. The #! is actually a two-byte "magic number", a special marker that designates a file type, or in this case an executable shell script [...]"

(Source: Advanced Bash-Scripting Guide)

4

Just to add, (I came to know this, sometimes back with-in this forum)

if you invoke a script with the shell command line,
e.g

ksh some_script.sh

the sha-bang in the some_script.sh will be ignored and the script will be executed with ksh.