Select between curl(1), wget(1), and ftp(1) through autoconf.
Wherever possible, automatically follow HTTP location redirects and
enable passive FTP mode.
Explicitly instruct tar(1) to read from stdin since this is far from
universal behavior if unspecified: The default file is /dev/sa0 in
FreeBSD, /dev/rst0 in NetBSD and OpenBSD, etc.
Tests for program presence, such as those formerly embedded in the
top-level Makefile for gawk and gsed, are better suited for autoconf.
Note that it is not sufficient to merely export AWK and SED environment
variables, as packages may still directly invoke awk(1) and sed(1) with
non-standard features independent of the autotools framework.
Wrapper scripts therefore remain necessary, although these are now
generated by the configure script to avoid hard-coded paths.
Do not assume the existence of /bin/bash on all systems.
Albert Ou
Palmer Dabbelt
Andrew Waterman