[R] search path question

[Prof Brian Ripley]

I meant essentially the same thing but returning file(fixed_up_name).
You can vectorize this BTW:

search_file <- function(name, path=getOption("scanpath"))
{
     fp <- c(name, file.path(path, name)) # better to use direct name first
     fp <- fp[file.exists(fp)]
     if(length(fp)) file(fp[1]) else stop(name, " not found")
}

Shortly things like

> read.table(search_file("passwd"))

will close the unnamed connection for you.

On Wed, 30 May 2007, Barry Rowlingson wrote:

> Prof Brian Ripley wrote:
>
>>
>> You could do this via a search_file() connection wrapper, but there is a
>> problem with ensuring connections get closed (which on.exit does here).
>>
>
>  I'm not sure exactly what you mean by a 'search_file() connection
> wrapper', but I have realised that its probably a better idea to write a
> function that checks a search path for a file and then returns that file:
>
> search_file =
> function(name,path=options()$scanpath,...){
> for(p in path){
>       file=file.path(p,name)
>       if(file.exists(file)){
>         return(file)
>       }
>     }
> return(name)
> }
>
>  Then you can use that in any filename-using function:
>
>  options(scanpath=c("/data1","/data2","/etc"))
>
>  > search_file("passwd")
>  [1] "/etc/passwd"
>
>  > passwd = read.table(search_file("passwd"),sep=":")
>  > record = scan(search_file("passwd"),what='')[1]
>
> Barry
>
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>

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595