Parses and returns the DESCRIPTION file of a package.
packageDescription(pkg, lib.loc = NULL, fields = NULL,
drop = TRUE, encoding = "")
packageVersion(pkg, lib.loc = NULL)a character string with the package name.
a character vector of directory names of R libraries,
or NULL. The default value of NULL corresponds to all
libraries currently known. If the default is used, the loaded
packages and namespaces are searched before the libraries.
a character vector giving the tags of fields to return (if other fields occur in the file they are ignored).
If TRUE and the length of fields is 1, then
a single character string with the value of the respective field is
returned instead of an object of class "packageDescription".
If there is an Encoding field, to what encoding
should re-encoding be attempted? If NA, no re-encoding. The
other values are as used by iconv, so the default
"" indicates the encoding of the current locale.
If a DESCRIPTION file for the given package is found and can
successfully be read, packageDescription returns an object of
class "packageDescription", which is a named list with the
values of the (given) fields as elements and the tags as names, unless
drop = TRUE.
If parsing the DESCRIPTION file was not successful, it returns
a named list of NAs with the field tags as names if fields
is not null, and NA otherwise.
packageVersion() returns a (length-one) object of class
"package_version".
A package will not be ‘found’ unless it has a DESCRIPTION file
which contains a valid Version field. Different warnings are
given when no package directory is found and when there is a suitable
directory but no valid DESCRIPTION file.
An attached environment named to look like a package
(e.g., package:utils2) will be ignored.
packageVersion() is a convenience shortcut, allowing things
like if (packageVersion("MASS") < "7.3") { do.things } .