I had an identical problem building in R.2.12 with the latest (last week's) Rtools.
Interestingly I found that if I used a DOS path in rcmd build (eg rcmd build 0.9\pkg) I got a .tar, but if I replaced it with the unix-like path as in rcmd build 0.9/pkg I got a .tar.gz Weird but workable. S Ellison LGC -- View this message in context: http://r.789695.n4.nabble.com/R-CMD-build-creates-tar-file-instead-of-tar-gz-file-tp3402687p3427046.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.