What is a shebang?

Question

Since in many languages the character # represents a committal, what is the sense of using it?

He has some special sense?

Answer 1

Yes, it has most Linux distributions. Indicates the interpreter that should be used to run a particular program/file.

Important (Remembered by our colleague @Wtrmute):

Because the "#" character is used as a comment marker in many scripting languages, the use of shebang in most cases will not interfere with the functioning of the code; in some language interpreters that do not use a wire to start comments (such as Scheme) can ignore the shebang line, in recognition of its purpose in some systems.

Giving the example with python, if you put in the first line of your prog.py

#!/usr/bin/env python

you can run this on the terminal just by doing ./prog.py (provided you give permissions for the system to run) where the first argument to enter the command #!/usr/bin/env python will be the file name itself, ie the command that at the bottom will happen is /usr/bin/env python prog.py and do not need to explain python prog.py at the terminal (where python in this case it is only one alias for /usr/bin/env python).

This answer from codegolf perfectly clarifies what I say.

Let’s do this for example and clarification:

Create the file ex.txt with the content "#!/bin/rm", and give the necessary permissions:

$ echo '#!/bin/rm' > ex.txt && chmod 777 ex.txt

Our ex.txt has at this time only and only (but could have what we want next) in the first line:

#!/bin/rm

Then we run the "program":

$ ./ex.txt

Nothing happened (we executed our "program").
Now let’s run it again:

$ ./ex.txt
bash: ./ex.txt: No such file or directory

What happened here was:

$ /bin/rm ex.txt

In which /bin/rm (that 'enters' as shebang), remove/delete the file/directory that comes as argument from the command, which is what you have the shebang defined/declared in its content.

Answer 2

In the case of scripting languages in Linux distributions, a script can start with the shebang which is the #!, plus the interpreter path to be used in the script ex.: #!/bin/bash.

Using an example with shell script, I can create a file script.sh where in the first line I place the shebang indicating /bin/bash as the interpreter.

#!/bin/bash
echo "Olá mundo"

When executing it after giving this execution permission (chmod a+x script.sh) will be verified which interpreter is indicated in shebang and the script will be executed internally as follows:

/bin/bash script.sh

For # be used as comment indication in various scripting languages, the use of shebang will not cause problems in the functioning of the code in most cases.

_{References:
Linux Shell Scripting Cookbook
Shebang - Wikipedia, the free encyclopedia}