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Re: A bug on cat command for zsh

Hi Andreas,

Thanks for pointing that out. 

Yep, I see such different behavior (just by chance when playing around with command line) from MacOS(which is BSD system) and Linux (which follows GNU). I think you’re right they have different implementations of `cat`.

Have a nice day!


> On Dec 4, 2023, at 12:01 AM, Andreas Kähäri <andreas.kahari@xxxxxx> wrote:
> 
> On Mon, Dec 04, 2023 at 07:01:42AM +0000, Wang, Yichao wrote:
>> Hi there,
>> 
>> I am using zsh 5.9 (x86_64-apple-darwin23.0) on MacOS.
>> 
>> The following command in zsh will cause severe damage by running forever into a dead loop.
>> - when you accidentally mess up the redirection flows
>> 
>> ```bash
>> touch 1.txt
>> echo "anything" > 1.txt
>> cat < 1.txt >> 1.txt
>> ```
>> 
>> However, on Linux bash, this behavior is prohibited and hinted.
>> 
>> ```bash
>> cat < 1.txt >> 1.txt
>> cat: -: input file is output file
>> ```
>> 
>> Best,
>> Unknown name
> 
> Allowing the programmer to shoot themselves in the foot does not
> seem like a bug to me.  Note that bash release 5.2.15 does not
> seem to babysit the user in the way that you describe by default.
> Rather, it's the coreutils implementation of cat that does this.
> 
> You may have two implementaions of cat on your system (it's possibly
> a BSD system, or at least non-GNU system, with coreutils installed
> alongside the native utilities).  Check with "type cat" in both shells
> to see what cat is being picked up.
> 
> 
> -- 
> Andreas (Kusalananda) Kähäri
> Uppsala, Sweden
> 
> .
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