Re: Cygwin 1.3.10 read command and W2K

Re: Cygwin 1.3.10 read command and W2K

[Gerald Reno]

bash version is 2.05a.0(3)

--- Gerald Reno <grenoml@yahoo.com> wrote:
> I have scripts with reads that are failing.  Why
> doesn't "echo text | read var; echo $var" work?  var
> is just empty.  Doesn't 'read' default to stdin? 
> All
> other commands seem to be working only read is
> having
> problem.
> 
> 
> 
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Re: Cygwin 1.3.10 read command and W2K

[Gerald Reno]

Ah yes, I had forgotten about the subshell.  Isn't
there a construction such as "echo text |& read -p
var" that will allow you to read into parent shell?


--- Randall R Schulz <rrschulz@cris.com> wrote:
> Gerald,
> 
> [ The usual disclaimer: None of this is Cygwin
> specific. ]
> 
> 
> When you use a pipe, the shell forks. In your
> example, the read command was 
> occurring in a forked sub-shell, and hence the
> side-effect on $var is not 
> seen in the shell that reads and interprets the
> pipeline you gave (and 
> subsequent commands).
> 
> Compare the output of this pipeline:
> 
> % echo foo |read bar; echo $bar
> 
> %
> 
> With that of this one:
> 
> % echo foo | (read bar; echo $bar)
> foo
> %
> 
> 
> Depending on the complexity of your script, this
> construct might work:
> 
> % bar="$(echo foo)"
> % echo $bar
> foo
> 
> 
> Randall Schulz
> Mountain View, CA USA
> 
> 
> 
> At 13:01 2002-06-06, Gerald Reno wrote:
> >I have scripts with reads that are failing.  Why
> doesn't "echo text | read 
> >var; echo $var" work?  var is just empty.  Doesn't
> 'read' default to 
> >stdin?  All other commands seem to be working only
> read is having problem.
> 


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Re: Cygwin 1.3.10 read command and W2K

[Randall R Schulz]

Gerald,

[ The usual disclaimer: None of this is Cygwin specific. ]


When you use a pipe, the shell forks. In your example, the read command was 
occurring in a forked sub-shell, and hence the side-effect on $var is not 
seen in the shell that reads and interprets the pipeline you gave (and 
subsequent commands).

Compare the output of this pipeline:

% echo foo |read bar; echo $bar

%

With that of this one:

% echo foo | (read bar; echo $bar)
foo
%


Depending on the complexity of your script, this construct might work:

% bar="$(echo foo)"
% echo $bar
foo


Randall Schulz
Mountain View, CA USA



At 13:01 2002-06-06, Gerald Reno wrote:
>I have scripts with reads that are failing.  Why doesn't "echo text | read 
>var; echo $var" work?  var is just empty.  Doesn't 'read' default to 
>stdin?  All other commands seem to be working only read is having problem.


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Cygwin 1.3.10 read command and W2K

[Gerald Reno]

I have scripts with reads that are failing.  Why
doesn't "echo text | read var; echo $var" work?  var
is just empty.  Doesn't 'read' default to stdin?  All
other commands seem to be working only read is having
problem.



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