Shell Script Shebang

The #! syntax is used in scripts to indicate an interpreter for execution under UNIX / Linux operating systems. The directive must be the first line in the Linux shell script and must start with shebang #!.

The sharp sign (#) and the bang sign (!) thats why called is the shebang. (sharpbang)

Shebang starts with #! characters and the path to the bash or other interpreter of your choice. Make sure the interpreter is the full path to a binary file. For example: /bin/bash.

#!/bin/bash
sleep 300

If a script does not contain a shebang the commands are executed using your shell.
you can print SHELL variable to show which shell you are using.
Different shells have slightly varying syntex
you can see all the available shells in /etc/shells file in Linux operating system.
It makes shell scripts more like actual executable files,
because they can be the subject of 'exec.'
If you do a 'ps' while such a command is running, the real name appears instead of 'sh' or 'bash'. Likewise, system accounting is done based on the real name.
It will allow other interpreters to fit in more smoothly.

                                                                                                                                                             
┌──(gaurav㉿learning-ocean)-[~/shellscript-youtube]
└─$ cat /etc/shells 
#!/bin/bash
#!/bin/python
#!/bin/sh
#!/usr/bin/perl
#!/usr/bin/tcl
#!/bin/sed -f
#!/bin/awk -f

let's run a script with other interpreter. create a file using the below snippts

#!/usr/bin/python
print("Hello this is python script")

now let's change the mode and give the execute permission to file. and execute it.

┌──(gaurav㉿learning-ocean)-[~/shellscript-youtube]
└─$ chmod +x second.sh                                                                                                                              
┌──(gaurav㉿learning-ocean)-[~/shellscript-youtube]
└─$ ./second.sh 
hello world from python program

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