[R] getting package version inside .First.lib

[Roger Bivand]

On Thu, 27 Jan 2005, Prof Brian Ripley wrote:

> On Thu, 27 Jan 2005, Adrian Baddeley wrote:
> 
> > Greetings -
> >
> > Is it possible, inside .First.lib,
> > to find out the version number of the package that is being loaded?
> >
> > If only one version of the package has been installed,
> > we could scan the DESCRIPTION file, something like
> >
> > .First.lib <- function(lib, pkg) {
> >    library.dynam("spatstat", pkg, lib)
> >    dfile <- system.file("DESCRIPTION", package="spatstat")
> >    ttt <- scan(dfile, what="", sep="^M", quiet=TRUE)[2]
> 
> "\n" not "^M", please, and readLines is better than scan here.
> 
> >    vvv <- strsplit(ttt," ")[[1]][2]
> >    cat("spatstat version number",vvv,"\n")
> > }
> >
> > but even this does not seem very safe (it makes assumptions about the
> > format of the DESCRIPTION file).
> 
> It is better to use read.dcf or the installed description information in 
> package.rds. Take a look at how library() does this.

Or even packageDescription() in utils, which uses read.dcf() and should be
a way of making sure you get the version even if the underlying formatting
changes.

Roger

> 
> Post R-2.0.0 you can assume the format is as library uses.
> 
> BTW: all installed.packages does is to read the descriptions of all the 
> packages it finds, and in .First.lib you know the path to your package.
> 
> 

-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Breiviksveien 40, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 93 93
e-mail: Roger.Bivand at nhh.no