Shebang

In my reading today I came across several references to shebangs From 
the references I've found it looks like a shebang is a way to make hard 
path reference to an executable like bash. Is this right or have I 
missed something? I thought people were trying to get hard coded paths 
out of their code.


	Have a Great Day!

	Pat	(tablepc)

[Samuel Sieb]

On 2/8/19 1:56 PM, pmkellly(a)frontier.com wrote:
>  In my reading today I came across several references to shebangs From
>
>  the references I've found it looks like a shebang is a way to make hard 
>  path reference to an executable like bash. Is this right or have I 
>  missed something? I thought people were trying to get hard coded paths 
>  out of their code. 
https://en.wikipedia.org/wiki/Shebang_(Unix)
The "#!" line at the start of a script that tells the OS what program to 
use to run it.

[Harold Dost]

I'd you're not sure the path of something you do have the option of using
#! /bin/env python
As an example so you don't require the entire path

On Fri, Feb 8, 2019, 17:06 Samuel Sieb <samuel(a)sieb.net&gt; wrote:

>  On 2/8/19 1:56 PM, pmkellly(a)frontier.com wrote:
>  > In my reading today I came across several references to shebangs From
>  > the references I've found it looks like a shebang is a way to make hard
>  > path reference to an executable like bash. Is this right or have I
>  > missed something? I thought people were trying to get hard coded paths
>  > out of their code.
>
>  https://en.wikipedia.org/wiki/Shebang_(Unix)
>  The "#!" line at the start of a script that tells the OS what program to
>  use to run it.
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[Michal Jaegermann]

On Fri, Feb 08, 2019 at 04:56:12PM -0500, pmkellly(a)frontier.com wrote:
>  looks like a shebang is a way to make hard path
>  reference to an executable like bash. Is this right or have I missed
>  something? 
You missed something.  Samuel Sieb already replied with
reference.  You may use it like

  #!/usr/bin/env bash

which will look for bash in your PATH and similar with
other interpreters.

>  I thought people were trying to get hard coded paths out of their
>  code. 
Usually you DO NOT want to execute a program called
'bash' found somewhere instead of /bin/bash.  A script writer does not
control what will be found first in PATH.

Besides in the above you need '#!/usr/bin/env' as kernel knows nothing
about PATH.  You can more often encounter '#!/usr/bin/env python'
or something like that; this give more flexibility which 'python'
to use with trade-offs involved.


   Michal

[Anderson, Charles R]

On Fri, Feb 08, 2019 at 04:39:27PM -0700, Michal Jaegermann wrote:
>  On Fri, Feb 08, 2019 at 04:56:12PM -0500, pmkellly(a)frontier.com
> wrote:
>  > looks like a shebang is a way to make hard path
>  > reference to an executable like bash. Is this right or have I missed
>  > something?
>  
>  You missed something.  Samuel Sieb already replied with
>  reference.  You may use it like
>  
>    #!/usr/bin/env bash
>  
>  which will look for bash in your PATH and similar with
>  other interpreters.
>  
>  > I thought people were trying to get hard coded paths out of their
>  > code.
>  
>  Usually you DO NOT want to execute a program called
>  'bash' found somewhere instead of /bin/bash.  A script writer does not
>  control what will be found first in PATH.
>  
>  Besides in the above you need '#!/usr/bin/env' as kernel knows nothing
>  about PATH.  You can more often encounter '#!/usr/bin/env python'
>  or something like that; this give more flexibility which 'python'
>  to use with trade-offs involved. 
Current Fedora packaging guidelines prohibit using tricks like #!/usr/bin/env perl,
instead requiring #!/usr/bin/perl hardcoded paths for all scripts packaged and distributed
with Fedora.  In fact, the build process will fixup script shebang lines automatically.

https://pagure.io/packaging-committee/issue/700

https://docs.fedoraproject.org/en-US/packaging-guidelines/#_shebang_lines