[R] getting package version inside .First.lib

[Prof Brian Ripley]

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.

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.

-- 
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