scripts/grml-config.sh: check whether wget and/or curl are available …

…and fail on errors

On e.g. OS X wget isn't available but curl is, so check wget
is available, else try curl or otherwise report error.

While at it, fail early and on any error.

See updated version of
https://michael-prokop.at/blog/2007/12/22/make-console-work-comfortable/

scripts/grml-config.sh

@@ -1,9 +1,24 @@
 #!/bin/sh
+
+set -e
+
 # IMPORTANT: please note that you might override existing
-# configuration files in the current working directory! =>
-wget -O .screenrc     https://git.grml.org/f/grml-etc-core/etc/grml/screenrc_generic
-wget -O .tmux.conf    https://git.grml.org/f/grml-etc-core/etc/tmux.conf
-wget -O .vimrc        https://git.grml.org/f/grml-etc-core/etc/vim/vimrc
-wget -O .zshrc        https://git.grml.org/f/grml-etc-core/etc/zsh/zshrc
-# optional:
-# wget -O .zshrc.local        https://git.grml.org/f/grml-etc-core/etc/skel/.zshrc
+# configuration files in the current working directory!
+if command -v wget >/dev/null 2>&1 ; then
+  wget -O .screenrc     https://git.grml.org/f/grml-etc-core/etc/grml/screenrc_generic
+  wget -O .tmux.conf    https://git.grml.org/f/grml-etc-core/etc/tmux.conf
+  wget -O .vimrc        https://git.grml.org/f/grml-etc-core/etc/vim/vimrc
+  wget -O .zshrc        https://git.grml.org/f/grml-etc-core/etc/zsh/zshrc
+  # optional:
+  # wget -O .zshrc.local https://git.grml.org/f/grml-etc-core/etc/skel/.zshrc
+elif command -v curl >/dev/null 2>&1 ; then
+  curl -L -o .screenrc   https://grml.org/console/screenrc
+  curl -L -o .tmux.conf  https://grml.org/console/tmux.conf
+  curl -L -o .vimrc      https://grml.org/console/vimrc
+  curl -L -o .zshrc      https://grml.org/console/zshrc
+  # optional:
+  # curl -L -o .zshrc.local  https://git.grml.org/f/grml-etc-core/etc/skel/.zshrc
+else
+  echo 'Error: neither wget nor curl available for retrieving configuration files.' >&2
+  exit 1
+fi