3 ms·

It checks if the variables 'ls' and 'la' exist, and if they do, it'll run it as python. If not, it'll try to parse it as bash. If it can't parse it as bash, it'

by jonfw 6y ago

It checks if the variables 'ls' and 'la' exist, and if they do, it'll run it as python. If not, it'll try to parse it as bash. If it can't parse it as bash, it'll try again in python mode. https://xon.sh/tutorial.html#python-mode-vs-subprocess-mode https://xon.sh/tutorial.html#python-mode-vs-subprocess-mode

enriquto 6y ago
> It checks if the variables 'ls' and 'la' exist, and if they do, it'll run it as python. If not, it'll try to parse it as bash. This is horrifying. It can break in so many unexpected and context dependent ways... Do people really run this shell on purpose?
- jonfw 6y ago
  There are edge cases but IME I rarely came across commands that could be valid python and valid bash. And you'll keep those in mind when you're running things so that you won't ever name a variable after a bash command you might use. I ran it for a couple of years while I was in school, it worked great. I wouldn't run it on a production server, this is really for experimental work
- BeetleB 6y ago
  I've been using it for a few years. It has its warts, but the problem you highlighted has never bitten me.
- IgorPartola 6y ago
  Holy crap that was my exact reaction to reading that. It’s just like bash: 99% of the time it’s an innocent thing, until suddenly you source some script that redefines something, innocently thinking it shouldn’t be a problem. That’s how you get an rm -rf.
  - jonfw 6y ago
    Yeah you wouldn't source a script written for a different shell in this language, if that's a part of your workflow you'll want to either audit them first or you'll just want to drop into a bash shell. I'm not sure how you end up rm -rf ing anything. 'rm -rf' by itself doesn't do anything, and if you do 'rm -rf .' that's no longer valid python. Not to mention that most people writing python would write 'rm - rf' if for some reason they had variables with those names (why would you name it that?) that they needed to subtract. And for some reason, you're not doing anything with the result of that subtraction. If you're sourcing scripts without reading them, the source of the danger is that behavior, not your shell
    - enriquto 6y ago
      > most people writing python would write 'rm - rf' if for some reason they had variables with those names (why would you name it that?) that they needed to subtract. I can see myself naming variables that way, when doing a geometric computation. Being a mathematician, all my variable names are single letters. But sometimes I have variants of a name that merit a second letter, like a sub-index. Maybe I use "r" for the current radius of an object and "rm" for the "middle" radius and "rf" for the "final" radius after some polishing process. Then I want to see how much material I'm losing from the object in the middle. Thus "rm -rf" (yes, the missing space is a typo).
      - jonfw 6y ago
        You need two typos in that you need to forget that space, and you also need to have forgotten to set one of those variables. You also don't actually delete anything until you name a file, so you'll need to add more valid python that's also a valid filename

by jonfw 6y ago

enriquto 6y ago

> It checks if the variables 'ls' and 'la' exist, and if they do, it'll run it as python. If not, it'll try to parse it as bash. This is horrifying. It can break in so many unexpected and context dependent ways... Do people really run this shell on purpose?

jonfw 6y ago
There are edge cases but IME I rarely came across commands that could be valid python and valid bash. And you'll keep those in mind when you're running things so that you won't ever name a variable after a bash command you might use. I ran it for a couple of years while I was in school, it worked great. I wouldn't run it on a production server, this is really for experimental work
BeetleB 6y ago
I've been using it for a few years. It has its warts, but the problem you highlighted has never bitten me.
IgorPartola 6y ago
Holy crap that was my exact reaction to reading that. It’s just like bash: 99% of the time it’s an innocent thing, until suddenly you source some script that redefines something, innocently thinking it shouldn’t be a problem. That’s how you get an rm -rf.
- jonfw 6y ago
  Yeah you wouldn't source a script written for a different shell in this language, if that's a part of your workflow you'll want to either audit them first or you'll just want to drop into a bash shell. I'm not sure how you end up rm -rf ing anything. 'rm -rf' by itself doesn't do anything, and if you do 'rm -rf .' that's no longer valid python. Not to mention that most people writing python would write 'rm - rf' if for some reason they had variables with those names (why would you name it that?) that they needed to subtract. And for some reason, you're not doing anything with the result of that subtraction. If you're sourcing scripts without reading them, the source of the danger is that behavior, not your shell
  - enriquto 6y ago
    > most people writing python would write 'rm - rf' if for some reason they had variables with those names (why would you name it that?) that they needed to subtract. I can see myself naming variables that way, when doing a geometric computation. Being a mathematician, all my variable names are single letters. But sometimes I have variants of a name that merit a second letter, like a sub-index. Maybe I use "r" for the current radius of an object and "rm" for the "middle" radius and "rf" for the "final" radius after some polishing process. Then I want to see how much material I'm losing from the object in the middle. Thus "rm -rf" (yes, the missing space is a typo).
    - jonfw 6y ago
      You need two typos in that you need to forget that space, and you also need to have forgotten to set one of those variables. You also don't actually delete anything until you name a file, so you'll need to add more valid python that's also a valid filename