R help - Aug 2005 - how to close connections?

Hi everybody,

I am using gzipped files quite extensively and cannot figure out how I
can close (or reuse) connections.  

Example:
> for(i in 1:300) {cat(i, "\n"); a <-
readLines(gzfile("file.gz"), n=1) }
1 
2 
...
46 
47 
Error in gzfile("~/tyyq/andmebaasiq/ETU/ETU1997.tsv.gz") : 
	all connections are in use

To use just gzfile without any open/close should be OK as the help
states:

... In general functions using connections will open them if they are not
open, but then close them again, so to leave a connection open call
open explicitly.

I have also experimented with explicit open/close but without any more
success, though, R claims that the connections will be closed.

Any ideas?  Is it my misunderstanding?  What exactly means a
connection is "in use"?

Thanks in advance,

Ott
> version
         _                
platform i686-pc-linux-gnu
arch     i686             
os       linux-gnu        
system   i686, linux-gnu  
status                    
major    2                
minor    1.1              
year     2005             
month    06               
day      20               
language R                




-- 
Ott Toomet, PhD
Research Fellow

Dept. of Economics
Tartu University
Narva 4 - A123
Tartu 51009
Estonia

otoomet (a) ut ee
ph:  (+372) 7 37 6374
fax: (+372) 7 37 6312
-------------------------------------------

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//\         //\         //\         //\      
V_/_        V_/_        V_/_        V_/_     
					     
standard    drunken     shocked     noisy    
penguin     penguin     penguin     penguin

Try this

con <- gzfile("file.gz")
a <- readLines(con, n=1)
showConnections(all=TRUE)
close(con)
showConnections(all=TRUE)

So the connection is opened and closed as it says, but not destroyed.
You do need to call close() explicitly -- from the help file

      'close' closes and destroys a connection.
                     ^^^^^^^^^^^^

There are  'create - open - close - destroy'  states for a connection.


On Thu, 25 Aug 2005, Ott Toomet wrote:
> Hi everybody,
>
> I am using gzipped files quite extensively and cannot figure out how I
> can close (or reuse) connections.
>
> Example:
>
>> for(i in 1:300) {cat(i, "\n"); a <-
readLines(gzfile("file.gz"), n=1) }
> 1
> 2
> ...
> 46
> 47
> Error in gzfile("~/tyyq/andmebaasiq/ETU/ETU1997.tsv.gz") :
> 	all connections are in use
>
> To use just gzfile without any open/close should be OK as the help
> states:
>
> ... In general functions using connections will open them if they are not
> open, but then close them again, so to leave a connection open call
> open explicitly.
>
> I have also experimented with explicit open/close but without any more
> success, though, R claims that the connections will be closed.
>
> Any ideas?  Is it my misunderstanding?  What exactly means a
> connection is "in use"?
-- 
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