Re: why does </proc/self/environ not work in bash?

[Chet Ramey]

On 2/10/24 11:00 PM, Christoph Anton Mitterer wrote:
> Hey there.
>
> I stumbled over something which I cannot really explain:

It depends on the behavior of the /proc driver.

> Doing e.g.:
>    $ tr '\000' '\n' </proc/self/environ
> in bash gives no output, while e.g. in dash
> it gives the env vars, as I'd have expected it.
>
> First question here is: whose environment should/would it return? The
> shell's? tr's?
> I'd assume the former, because the shell sets up the redirection

A system call tracer helps here. You'll find that the shell forks,
sets up the redirection by opening /proc/self/environ, then execs tr,
which reads the open file descriptor it inherits through execve. Does
the /proc driver invalidate the inherited file descriptor?

--
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/

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