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Re: [UX] real names exposed
From: |
Troy Sankey |
Subject: |
Re: [UX] real names exposed |
Date: |
Sat, 03 Sep 2016 11:30:18 -0400 |
User-agent: |
alot/0.3.7 |
Quoting Ludovic Courtès (2016-09-01 04:59:02)
> ‘exec -a’ works as advertised:
>
> --8<---------------cut here---------------start------------->8---
> $ sh -c 'exec -a FOO guile -c "(pk (command-line))"'
>
> ;;; (("FOO"))
> --8<---------------cut here---------------end--------------->8---
So, here /proc/self/cmdline would be: guile\0
and bash changed it to: FOO\0
> Yet:
>
> --8<---------------cut here---------------start------------->8---
> $ sh -c 'exec -a FOO
> /gnu/store/6vmniz83k46l8jpry50wdvwxsncz1r5w-khal-0.7.0/bin/.khal-wrap-01
> --version'
> .khal-real, version 0.7.0
> --8<---------------cut here---------------end--------------->8---
here it's: python3\0.khal-real\0--version\0
bash changed it to: FOO\0.khal-real\0--version\0
> And in fact:
>
> --8<---------------cut here---------------start------------->8---
> $ cat > t.py
> import sys
> print(sys.argv[0])
> $ sh -c 'exec -a FOO python3 t.py'
> t.py
> --8<---------------cut here---------------end--------------->8---
here it's: python3\0t.py\0
bash changed it to: FOO\0t.py\0
> … even though argv[0] is initially correct:
>
> --8<---------------cut here---------------start------------->8---
> $ sh -c 'exec -a FOO python3 --help' | head -1
> usage: FOO [option] ... [-c cmd | -m mod | file | -] [arg] ...
> --8<---------------cut here---------------end--------------->8---
>
> So somewhere, Python finds out the real name, but it doesn’t seem to be
> via /proc/cmdline or anything like that, and I couldn’t find the exact
> hack in the source.
>
> Ideas?
Seems that there is no reason to think python doesn't simply use
/proc/self/cmdline. Before script interpretation, but after spawning,
the python interpreter appears to modify the arguments list to hide the
first element:
argv = argv[1:] # I made this up, but it's probably something like this
> I would really like to fix it in ‘core-updates’.
>
> Ludo’.
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