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What is passing the usr bin env for in the shebang?
In addition to the answers given above, the use of /usr/bin/env allows your Python to be installed in non-standard places, and as long as your PATH is set-up correctly, the script will run unmodified on any UNIX-style system that has /usr/bin/env . This includes any modern version of Linux and OS/X.
Is shebang a Posix?
If you’re writing POSIX shell scripts for common Unix and Linux operating systems, simply use #!/bin/sh as the shebang. In rare cases where /bin/sh is a Bourne shell instead of a POSIX-compliant shell, you would have to modify the shebang to use the appropriate full path to the POSIX shell.
What is bin sh used for?
/bin/sh is an executable representing the system shell and usually implemented as a symbolic link pointing to the executable for whichever shell is the system shell. The system shell is basically the default shell that the script should use.
Why do we write #!/ bin sh?
#!/bin/sh or #!/bin/bash has to be first line of the script because if you don’t use it on the first line then the system will treat all the commands in that script as different commands.
What does #!/ Usr bin env SH do?
Using #!/usr/bin/env NAME makes the shell search for the first match of NAME in the $PATH environment variable. It can be useful if you aren’t aware of the absolute path or don’t want to search for it. If the shell scripts start with #!/bin/bash , they will always run with bash from /bin .
What is usr bin env for?
Therefore, /usr/bin/env python3 is an instruction to set the PATH (as well as all the other NAME+VALUE pairs), and then run python3 , using the first directory in the PATH that contains the python3 executable.
What does shebang mean in English?
: everything involved in what is under consideration —usually used in the phrase the whole shebang.
What’s the difference between bin / sh and bin / bin / env?
I never have seen this with sh. Setting to #!/bin/sh will go directly to that file /bin/sh. Setting to #!/usr/bin/env sh will execute /usr/bin/env with an argument of sh. This will cause the script to be executed by sh in your PATH variable rather than explicitly with /bin/sh.
Why is the “-” in the ” # bin / sh-” Shebang?
As on most systems the shebang mechanism allows only one argument after the interpreter path. As to whether to use #! /bin/sh – vs #!/bin/sh -, that’s just a matter of taste. I prefer the former as it makes the interpreter path more visible and makes mouse selection easier.
Why is # ! / usr / bin / env Bash superior to?
Is there any other reason to prefer #!/usr/bin/env bash over the alternatives and, assuming portability was a concern, is there any reason using it could break functionality? #!/usr/bin/env searches PATH for bash, and bash is not always in /bin, particularly on non-Linux systems.
Why is the shell script # ! / bin / sh-recommended?
Now beside the theoretical correctness issue, there’s another reason why #! /bin/sh – became recommended as good practice. And that goes back to a time where several systems still supported setuid scripts. And that script was setuid root (like with -r-sr-xr-x root bin permissions), on those systems, when executed by an ordinary user, the