The format of a 'shebang' interpreter directive is as follows
#!interpreter [optional-arg]
Shell-Script usually begins with one of the following typical line:
- #!/bin/bash - Execute the file using the
Bash shell - #!/bin/ksh - Execute the file using the
Korn shell - #!/bin/sh - Execute the file using the
Bourne shell, or a compatible shell, assumed to be in the /bin directory - #!/usr/bin/env bash - Execute the file using the
Bash shell - #!/usr/bin/env sh - Execute the file using the
Bourne shell, or a compatible shell, assumed to be in the /bin directory - #!/usr/bin/env python - Execute with a
Python interpreter, using the env program search path to find it - #!/usr/bin/pwsh - Execute the file using
PowerShell - #!/bin/false -
Do nothing, but return a non-zero exit status, indicating failure.
Used to prevent stand-alone execution of a script file intended for execution in a specific context,
such as by the.command from sh/bash,sourcefrom csh/tcsh, or as a .profile, .cshrc, or .login file
This first line (#!/bin/bash or #!/bin/sh) has a name.
It is known as 'she-bang'(shabang) or also sometimes called as 'hashbang' or 'Interpreter Directive'
Among, all the above formats, the best practice is as follows:
#!/usr/bin/env bash
#!/usr/bin/env sh
#!/usr/bin/env python
portability issues:
there are unix systems, where the default 'env' is not present in standard location like /usr/bin/env rather it's found under /bin/env,
in such cases, the script files won't run as expected bcoz it'd be unable to find the interpreter from the shebang declaration,
References:
https://en.wikipedia.org/wiki/Shebang_%28Unix%29
https://askubuntu.com/a/88314
https://unix.stackexchange.com/a/87600
https://stackoverflow.com/a/13872064