| zpackages {base} | R Documentation | 
.packages returns information about package availability.
.packages(all.available = FALSE, lib.loc = NULL)
all.available | 
logical; if TRUE return a character vector
of all available packages in lib.loc. | 
lib.loc | 
a character vector describing the location of R
library trees to search through, or NULL.  The default value
of NULL corresponds to all libraries currently known. | 
.packages() returns the “base names” of the currently
attached packages invisibly whereas
.packages(all.available = TRUE) gives (visibly) all
packages available in the library location path lib.loc.
For a package to be regarded as being available it must have a
‘DESCRIPTION’ file containing a valid version field.
A character vector of package “base names”, invisible unless
all.available = TRUE.
R core;
Guido Masarotto for the all.available=TRUE part of
.packages.
(.packages())               # maybe just "base"
.packages(all = TRUE)       # return all available as character vector
require(splines)            # the same
(.packages())               # "splines", too
detach("package:splines")