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Re: I think bash logic in a loop like : while [ condition] |read somevar


From: Pierre Gaston
Subject: Re: I think bash logic in a loop like : while [ condition] |read somevar is flawed.
Date: Wed, 25 Dec 2013 08:33:33 +0200

On Tue, Dec 24, 2013 at 8:56 PM, Greg Wooledge <address@hidden> wrote:

> On Tue, Dec 24, 2013 at 07:49:28PM +0100, rens wrote:
> > I understand the technical origin of the behaviour.
> > Spend +25 yrs in unix. I am so old, that I remember fighting (at my
> > 40th)  with linux 0.79, I think....
> >
> > However, I am questioning if this is what a programming language should
> do.
>
> Stop thinking of bash as a programming language.  It is a command shell.
>
> Pipelines invoke multiple processes simultaneously.  That's their purpose:
> to run a bunch of things in parallel, with linked input/output.  Each
> process is just that -- a process.  A full-blown separate running program
> with its own PID, its own private memory and file descriptors, and so on.
>
> Moreover, the behavior of bash is constrained by 40+ years of unix shell
> history.  It implements the feature set specified by POSIX, as well as
> doing its best to be backwards compatible with older versions of itself,
> and to a much smaller extent, with ksh and sometimes even csh.
>
> If you want a shell that breaks out of that mold and does things in a
> new way, then perhaps you want zsh.
>
> If you want an interpreted programming language instead of a shell,
> there are a bunch to choose from.
>
>
If I remember correctly, POSIX allows the lastpipe behaviour.

As far as not explaining the behaviour, mr rens clearly said he was not
interested in any kind of understanding.


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