Re: [Help-bash] confused by command substitution...

[David Niklas]

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On Mon, 11 Feb 2019 11:50:26 -0500
Greg Wooledge <address@hidden> wrote:
> On Sat, Feb 09, 2019 at 06:01:53AM -0500, Alfred M. Szmidt wrote:
> > I'm not understanding the difference here, or why the last example
> > works.  Anyone got a good explanation?
> > 
> > $ if "$(echo x)"; then echo foo; fi
> > bash: x: command not found
> > $ if "$(echo x > /dev/null)"; then echo foo; fi
> > bash: : command not found
> > $ if $(echo x); then echo foo; fi
> > bash: x: command not found
> > $ if $(echo x > /dev/null); then echo foo; fi
> > foo  
> 
> They're all 100% wrong.  If one of them happens not to throw a syntax
> error, that's just bash's way of lulling newbies into complacency so
> that their scripts blow up LATER instead of IMMEDIATELY.  Obviously a
> script that APPEARS to work has a better chance of going into production
> in a broken state.  This maximizes the chances of chaos and destruction.
> Bash craves these things.  The suffering of fools is its lifeblood.

ROFL

On Mon, 11 Feb 2019 11:50:26 -0500
Greg Wooledge <address@hidden> wrote:
> On Mon, Feb 11, 2019 at 11:45:58AM -0500, Alfred M. Szmidt wrote:
> <snip>
> > 
> >    They're all 100% wrong.  
> >    
> > Clearly they aren't.  They are also syntatically valid according to
> > POSIX grammar rules from what I can see.  
> 
> A syntactically parseable command can still be wrong, if it does not
> do what it's supposed to do.
> 
> What is "x"?  Why are you echoing it?  Why are you capturing the result
> of that echo and executing it as a second command?  What is the
> significance of the exit status of "x" which is apparently the
> secondary command you wish to execute?
> 
> Why are you not simply executing x directly?
> 
> What are you trying to do?
> 
> Why are you brushing me off and telling me to calm down instead of
> presenting a question that people can actually help you with?

We are like bash. We send you senseless problems to drive you to the edge
of your sanity, then we send a halt-and-catch-fire instruction your CPU,
and then you.. are.. ours! Mwha! Ha! Ha! Ha!

Hope my message is equally funny,
David
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