My application, at least, wanted to show (my class) individual commands 
from the file and then optionally insert some typed commands before 
going on to the next part of the source file. As far as I can see, the 
piped shell command approach will have to treat the whole file at one time.

John

Peter Dalgaard wrote:
> One canonical way of doing it is:
>
> (echo 'print(readline("Input:"))'; cat -) | R --interactive --no-save
>
> (you don't want to leave out --no-save ....)
>
>
> John Chambers wrote:
>   
>> For an alternative approach to your original goal, take a look at
>> demoSource() in the SoDA package from CRAN.  It's a bit tedious to set
>> up (see the Details section of the help file) but uses standard R
>> sessions to mix lines from a demo file and interactive input.
>>
>> John
>>
>> Jon Clayden wrote:
>>     
>>> Dear all,
>>>
>>> I have asked before, in R-help [1], about a way to create an
>>> interactive session in which commands are taken from a file or
>>> standard input - like R CMD BATCH but additionally allowing user
>>> input - but there was no response to that question, and the
>>> workarounds that I have found (using "expect", creating a temporary
>>> .Rprofile) are ugly and problematic.
>>>
>>> With the appearance of the --interactive flag in R 2.7.0 I thought
>>> this might become possible, but it not only does not behave as I
>>> would expect, it appears to go into an infinite loop, and uses 100%
>>> CPU until killed.
>>>
>>> $ echo 'print(readline("Input:"))' | R --no-save --quiet
>>>       
>>>> print(readline("Input:"))
>>>>         
>>> Input:[1] ""
>>>       
>>> [no interactivity]
>>>
>>> $ echo 'print(readline("Input:"))' | R --no-save --quiet --interactive
>>> [no response at all]
>>>
>>> This behaviour remains in the latest alphas of R 2.8.0. My platform
>>> is Mac OS X.5.5 on Intel Core 2 Duo.
>>>
>>> I assume, given this outcome, that this is not the intended use of
>>> --interactive, but I still wonder if there is any way to achieve an
>>> interactive session based on a predefined set of commands without
>>> writing a completely new front-end (overkill, surely?).
>>>
>>> Any guidance would be appreciated.
>>>
>>> Regards,
>>> Jon
>>>
>>> [1] http://finzi.psych.upenn.edu/R/Rhelp02a/archive/117412.html
>>>
>>>
>>> -- 
>>> Jonathan D. Clayden, Ph.D.
>>> Research Fellow
>>> Radiology and Physics Unit
>>> UCL Institute of Child Health
>>> 30 Guilford Street
>>> LONDON  WC1N 1EH
>>> United Kingdom
>>>
>>> t | +44 (0)20 7905 2708
>>> f | +44 (0)20 7905 2358
>>> w | www.homepages.ucl.ac.uk/~sejjjd2/
>>>
>>> ______________________________________________
>>> R-devel@r-project.org mailing list
>>> https://stat.ethz.ch/mailman/listinfo/r-devel
>>>
>>>       
>> ______________________________________________
>> R-devel@r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-devel
>>     
>
>
>   

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