getgo

#!/usr/bin/env bash
set +vx
# getgo - Install latest go(lang)

# Usage getgo [<version>]
# Required: wget sudo tar coreutils(mktemp mv rm tail)
# When TMPDIR is set, it is used for the temporary directory

goloc=/usr/local  # Install location for the go tree

Abort(){ # $1:message
	echo "ABORT: $1"
	exit 1
}

Sudo(){ # $1:prompt $2..:command
	local prompt="Privileges required" sudo=
	[[ $1 ]] && prompt+=" $1:" || prompt+=':'
	shift
	((EUID)) && ! sudo=$(type -p sudo) &&
		Abort "privileges required but 'sudo' not available"
	$sudo -nv &>/dev/null || echo "$prompt"
	$sudo $@
}

ver=$1
[[ ${ver//[.0-9]} ]] &&
	Abort "Version should only contain numbers and a dot, not: $ver"

os=${GO_OS:-Linux} os=${os,,}
[[ $(uname -m) = armv7l ]] && arch=armv6l || arch=amd64
: ${arch:=$GO_ARCH}
: ${ver:=$GO_VERSION}
[[ -z $ver ]] &&
	url=$(wget -qO- "https://golang.org/dl" |grep -o "[^\"]*\.$os-$arch\.tar\.gz" |head -1) &&
	ver=${url%.$os-$arch.tar.gz} ver=${ver#/dl/go}
# Use the discovered or specified $ver
dl="go$ver.$os-$arch.tar.gz"
url="https://golang.org/dl/$dl"
echo "Installing go $ver on $arch $os"
tmp=$(mktemp -d --tmpdir=$TMPDIR)
trap "Sudo 'to cleanup' rm -rf -- '$tmp'" QUIT EXIT
wget -qO "$tmp/$dl" "$url" || Abort "could not download go"
tar xf "$tmp/$dl" -C "$tmp" || Abort "error unpacking $dl to $tmp"
	Sudo 'to make root' chown root:root -R -- "$tmp"

# Move install directory if it exists already
if [[ -d $goloc/go ]]
then
	Sudo 'to move old go directory' mv -v -- "$goloc/go" \
			"$goloc/$($goloc/go/bin/go version |cut -f3 -d' ')_old$RANDOM" ||
		Abort "could not move $goloc/go out of the way"
fi
Sudo 'to install go directory' mv -v -- "$tmp/go" "$goloc" ||
	Abort "could not move $tmp/go to $goloc"
a="p='$goloc/go/bin' && [[ :\$PATH: != *:\$p:* ]] && export PATH=\$p:\$PATH"
[[ $GOROOT ]] || a+="\nexport GOROOT='$goloc/go'"
[[ $GOBIN ]] || a+="\nexport GOBIN=\$HOME/go/bin"
echo "Right now: GOROOT=$GOROOT GOBIN=$GOBIN PATH=$PATH"
export GOROOT="$goloc/go" GOPATH=~/go
echo -e "Add to ~/.bashrc:\n\n$a"
eval "${a//\\n/;}"

exit 0