Re: script relative shebang
I still think it is a good thing to do. I will try to implement it on github and may be some day someone influential will help me with that :) On 2 June 2016 05:19:34 BST, Ken Moffat wrote: >On Thu, Jun 02, 2016 at 01:04:46AM +0100, Boris Rybalkin wrote: >> Sorry for insisting, but I would like to explore potential solutions >> for fixing the root problem (missing relative shebang), >> I know there are ways to workaround that, but I would like to make >> sure the proper fix is not possible. >> I understood that it is too late to introduce additional keywords >> after #! as existing systems expect fs path there, OK. >> But what about changing #! itself, is it possible to introduce >another >> special sequence like #? to denote a relative mode: >> >> #?python/bin/python >> >If you are able to get that accepted, it will only work on linux >systems running such recent kernels. For your own systems, you can >of course do whatever you wish. But for public availability you >will then need to wait several years until your target linux users >can be expected to have moved to a suitable kernel (presumably the >*next* long-term stable kernel after the change is accepted : I >guess that version is perhaps the best part of a year away even if >your change got accepted into 4.8, and then you need your users' >distros to move to it). > >To me, that doesn't seem worth the trouble (to you) of coding it, >getting it reviewed and eventually accepted, and then fixing up >whatever problems arise after it gets into linux-next [ problems >will always appear, even if the new code turns out not to be the >cause ]. > >And first, you have to persuade somebody influential that this is a >good thing to do, particularly when people have suggested >alternative approaches. I don't count, but at the moment I've not >seen any good reasons why the kernel should be changed to support >this. > >But it's your time, and your itch to scratch. > >ĸen -- Sent from my Android device with K-9 Mail. Please excuse my brevity.
Re: script relative shebang
On Thu, Jun 02, 2016 at 01:04:46AM +0100, Boris Rybalkin wrote: > Sorry for insisting, but I would like to explore potential solutions > for fixing the root problem (missing relative shebang), > I know there are ways to workaround that, but I would like to make > sure the proper fix is not possible. > I understood that it is too late to introduce additional keywords > after #! as existing systems expect fs path there, OK. > But what about changing #! itself, is it possible to introduce another > special sequence like #? to denote a relative mode: > > #?python/bin/python > If you are able to get that accepted, it will only work on linux systems running such recent kernels. For your own systems, you can of course do whatever you wish. But for public availability you will then need to wait several years until your target linux users can be expected to have moved to a suitable kernel (presumably the *next* long-term stable kernel after the change is accepted : I guess that version is perhaps the best part of a year away even if your change got accepted into 4.8, and then you need your users' distros to move to it). To me, that doesn't seem worth the trouble (to you) of coding it, getting it reviewed and eventually accepted, and then fixing up whatever problems arise after it gets into linux-next [ problems will always appear, even if the new code turns out not to be the cause ]. And first, you have to persuade somebody influential that this is a good thing to do, particularly when people have suggested alternative approaches. I don't count, but at the moment I've not seen any good reasons why the kernel should be changed to support this. But it's your time, and your itch to scratch. ĸen -- I had to walk fifteen miles to school, barefoot in the snow. Uphill both ways.
Re: script relative shebang
Sorry for insisting, but I would like to explore potential solutions for fixing the root problem (missing relative shebang), I know there are ways to workaround that, but I would like to make sure the proper fix is not possible. I understood that it is too late to introduce additional keywords after #! as existing systems expect fs path there, OK. But what about changing #! itself, is it possible to introduce another special sequence like #? to denote a relative mode: #?python/bin/python -- Boris Rybalkin ribal...@gmail.com
Re: script relative shebang
On 2016-06-01 04:00, Boris wrote:
Hi Nicolai,
Yes, I think this is too ugly:
#!/usr/bin/gawk {exit system("/bin/sh -c 'exec \"$(dirname \"$0\")\"/subdir/catself
\"$0\"' " FILENAME);}
Imagine you have that feature in your kernel would you rather use:
#!{dirname}/subdir/catself
The problem with using a keyword is that current VFS standards on Linux
mean that most filesystems that are native to Linux support _any_
character in a path name component except for a null byte. Because of
that, you can't from a practical perspective choose a keyword that is
guaranteed to not clash with any path name, unless you want a 256
character long keyword (which would be worse than the current option).
You second advice involves changing root fs which is not desirable in
copy-deployment apps (bring all the dependencies)
Not necessarily, include the wrapper in the app itself. It's not hard
even in shell script to figure out where you're being run from, so it's
really not all that hard to handle this.
In bash, you can do the following in a script to get the canonical path
to you're script (in an interactive shell, it will just point you at the
bash executable):
SELF=$_
SELF=$(realpath ${SELF})
This only works if it's done at the top level of a script (not within a
function).
If you go with the wrapper option, you can find your canonical path name
in /proc/self/exe (note that this won't work right when doing something
like `readlink /proc/self/exe` from an interpreter, as that will return
the path to readlink), or just look up your PID and check /proc/PID/exe.
Also, the convention for such things on most UNIX like systems is to
install wrappers, often using symlinks, in some location that is listed
in $PATH. For example, on many Linux systems, Dropbox gets installed
into /opt/dropbox, and then a link for it is created in /opt/bin to
point at the core program itself. If it's a GUI only app, you could
also just use .desktop files to point at the tools instead of symlinks,
Google Chrome does this for example.
Using the bash example above, the following snippet could be used as a
wrapper by placing it the top level directory of the above example and
then symlinking to it from somewhere in $PATH:
#!/bin/bash
SELF=$_
SOURCE=$(dirname $(realpath ${SELF}))
exec ${SOURCE}/subdir/catself $@
You could then use that script as your interpreter.
Re: script relative shebang
Hi all!
On Wed, 2016-06-01 at 09:00 +0100, Boris wrote:
[...]
> Yes, I think this is too ugly:
>
> #!/usr/bin/gawk {exit system("/bin/sh -c 'exec \"$(dirname
> \"$0\")\"/subdir/catself \"$0\"' " FILENAME);}
The simplest solution for an application today is to provide a wrapper
script/program (to be placed in /usr/bin or /usr/local/bin) which knows
where to search for the applications executables - if adding some
directories to $PATH is not enough.
> Imagine you have that feature in your kernel would you rather use:
>
> #!{dirname}/subdir/catself
And what if "{dirname}" (or any other character sequence) happens to be
a valid pathname?
> You second advice involves changing root fs which is not desirable in
> copy-deployment apps (bring all the dependencies)
>
> This more about making kernel "user" friendly.
User-friendlyness is not the job of the kernel ...
[ Fullquote deleted as it's a bad habit ]
MfG,
Bernd
--
Bernd Petrovitsch Email : be...@petrovitsch.priv.at
LUGA : http://www.luga.at
Re: script relative shebang
Hi Nicolai,
Yes, I think this is too ugly:
#!/usr/bin/gawk {exit system("/bin/sh -c 'exec \"$(dirname
\"$0\")\"/subdir/catself \"$0\"' " FILENAME);}
Imagine you have that feature in your kernel would you rather use:
#!{dirname}/subdir/catself
You second advice involves changing root fs which is not desirable in
copy-deployment apps (bring all the dependencies)
This more about making kernel "user" friendly.
Thank you.
On 1 June 2016 00:02:05 BST, Nicolai Stange wrote:
>Hi Boris,
>
>Boris Rybalkin writes:
>
>> I would like to know if any changes to parsing '#!' script header
>line
>> are accepted in particular having ability to run interpreter from
>> relative to the script path?
>>
>> Something like:
>>
>> #!{dirname}/python/bin/python
>>
>> Where {dirname} is a special keyword replaced with dirname of a
>script.
>
>Just for the record, this can already be done without any help from the
>kernel:
>
>Assuming the following demonstration directory layout
>
> /subdir/catself
> /relshebang
>
>where catself.sh is your "interpreter":
>
> #!/bin/sh
> tail -n +2 $1
>
>and relshebang is your script file invoking the toy interpreter from
>its
>shebang as follows:
>
>#!/usr/bin/gawk {exit system("/bin/sh -c 'exec \"$(dirname
>\"$0\")\"/subdir/catself \"$0\"' " FILENAME);}
> Hello world.
>
>
>You don't necessarily need to use gawk here, anything being able to do
>system() and taking some code snippet from its first argument will
>certainly work.
>
>If this is too ugly, you could also write your own wrapper a la
>/usr/bin/env and install that at some central location.
>
>
>Best,
>
>Nicolai
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
Re: script relative shebang
Hi Boris,
Boris Rybalkin writes:
> I would like to know if any changes to parsing '#!' script header line
> are accepted in particular having ability to run interpreter from
> relative to the script path?
>
> Something like:
>
> #!{dirname}/python/bin/python
>
> Where {dirname} is a special keyword replaced with dirname of a script.
Just for the record, this can already be done without any help from the
kernel:
Assuming the following demonstration directory layout
/subdir/catself
/relshebang
where catself.sh is your "interpreter":
#!/bin/sh
tail -n +2 $1
and relshebang is your script file invoking the toy interpreter from its
shebang as follows:
#!/usr/bin/gawk {exit system("/bin/sh -c 'exec \"$(dirname
\"$0\")\"/subdir/catself \"$0\"' " FILENAME);}
Hello world.
You don't necessarily need to use gawk here, anything being able to do
system() and taking some code snippet from its first argument will
certainly work.
If this is too ugly, you could also write your own wrapper a la
/usr/bin/env and install that at some central location.
Best,
Nicolai
script relative shebang
Hi All,
I would like to know if any changes to parsing '#!' script header line
are accepted in particular having ability to run interpreter from
relative to the script path?
Something like:
#!{dirname}/python/bin/python
Where {dirname} is a special keyword replaced with dirname of a script.
This is useful for apps which bring dependencies with them and do not
want to hardcode absolute paths as target fs layout is not known or
has to be flexible.
As I understand the implementation is here and I could probably provide a patch:
fs/binfmt_script.c
Sorry if this is not the right place to discuss these things.
Thank you.
--
Boris Rybalkin
ribal...@gmail.com
