#! is the symbol that should be placed at the top of a Bash script to ensure it can be executed. #! is also known as shebang or hashbang. It is a special notation that tells the operating system which interpreter to use to run the script. The shebang is followed by the path to the interpreter, such as /bin/bash for Bash, /bin/python for Python, or /bin/perl for Perl. For example, a Bash script that prints “Hello World” would start with:

#!/bin/bash echo “Hello World”

The shebang must be the first line of the script and must not have any spaces between the # and ! symbols. bash is not a valid shebang by itself, as it does not specify the path to the interpreter. !execute is not a valid shebang at all, as it does not start with #. @echo off is a command that disables the echoing of commands in a batch file on Windows, but it has nothing to do with Bash scripts on Linux. References: https://www.howtogeek.com/67469/the-beginners-guide-to-shell-scripting-the-basics/ https://www.howtogeek.com/435903/what-is-a-shebang-line/