R package installer (handles specific versions)

gistfile1.r

#!/usr/bin/env Rscript

# Command line options parser.  Shamelessly stolen (and even then
# not well understood).
library('getopt');
spec = matrix(c(
  'package', 'p', 1, 'character',
  'version', 'v', 2, 'character',
  'help', 'h', 0, 'logical'
), byrow=TRUE, ncol=4);
opt = getopt(spec);

# Help, or, how to test your command-line options parser
if ( !is.null(opt$help) ) {
  cat(getopt(spec, usage=TRUE));
  q(status=1);
}

# Looks in the CRAN archive for the specified package and version. If
# the specified version is NULL or the same as the most recent version
# of the package, this function simply calls install.packages(). Otherwise,
# it looks at the list of archived source tarballs and tries to install
# an older version instead.

check.package.version <- function(package, version = NULL)
{
  gsub('-', '.', version) == tryCatch({packageVersion(package)}, error = function(cond) { return(FALSE) })
}

install.package.version <- function(package, version, repos = "http://cran.r-project.org", type = "source")
{
  contriburl <- contrib.url(repos, type)
  available <- available.packages(contriburl)
  if (package %in% row.names(available)) {
    current.version <- available[package, 'Version']
    if (is.null(version) || version == current.version) {
      install.packages(package, repos = repos, contriburl = contriburl, type = type)
      return()
    }
  }

  con <- gzcon(url(sprintf("%s/src/contrib/Meta/archive.rds", repos), "rb"))
  archive <- readRDS(con)
  close(con)

  info <- archive[[package]]

  if (is.null(info)) {
    stop(sprintf("couldn't find package '%s'", package))
  }

  if (is.null(version)) {
    # Just grab the latest one. This will only happen if the package
    # has been pulled from CRAN.
    # I don't think this code is ever called.
    package.path <- info[length(info)]
  } else {
    package.path <- paste(package, "/", package, "_", version, ".tar.gz", sep="")
    if (!(package.path %in% row.names(info))) {
      stop(sprintf("version '%s' is invalid for package '%s'", version, package))
    }
  }
  package.url <- sprintf("%s/src/contrib/Archive/%s", repos, package.path)
  local.path <- file.path(tempdir(), basename(package.path))
  if (download.file(package.url, local.path) != 0) {
    stop("couldn't download file: ", package.url)
  }

  options(install.packages.check.source = "no")
  install.packages(local.path, type = type)
}

if (!isTRUE(check.package.version(opt$package,opt$version))) {
  install.package.version(opt$package, opt$version)
}

Adapted from https://gist.github.com/viking/1503736