pfff. It's run without no problem with curl !!!
It's not a bashism. It exists on few shell, and run on ash too:
# echo $SHELL
/bin/ash
# v="19.07.5"
# curl -O https://downloads.openwrt.org/releases/"${v}"/targets/ramips/mt7621/{openwrt-"${v}"-ramips-mt7621-ubnt-erx-squashfs-sysupgrade.bin,sha256sums}
[1/2]: https://downloads.openwrt.org/releases/19.07.5/targets/ramips/mt7621/openwrt-19.07.5-ramips-mt7621-ubnt-erx-squashfs-sysupgrade.bin --> openwrt-19.07.5-ramips-mt7621-ubnt-erx-squashfs-sysupgrade.bin
--_curl_--https://downloads.openwrt.org/releases/19.07.5/targets/ramips/mt7621/openwrt-19.07.5-ramips-mt7621-ubnt-erx-squashfs-sysupgrade.bin
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 3560k 100 3560k 0 0 886k 0 0:00:04 0:00:04 --:--:-- 947k
[2/2]: https://downloads.openwrt.org/releases/19.07.5/targets/ramips/mt7621/sha256sums --> sha256sums
--_curl_--https://downloads.openwrt.org/releases/19.07.5/targets/ramips/mt7621/sha256sums
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 116k 100 116k 0 0 725k 0 --:--:-- --:--:-- --:--:-- 725k
# sha256sum -c sha256sums 2> /dev/null | grep OK
openwrt-19.07.5-ramips-mt7621-ubnt-erx-squashfs-sysupgrade.bin: OK
for those who focus on the "must" saying problem with brackets:
# wget https://downloads.openwrt.org/releases/19.07.5/targets/ramips/mt7621/openwrt-19.07.5-ramips-mt7621-ubnt-erx-squashfs-sysupgrade.bin
wget: SSL support not available, please install one of the libustream-.*[ssl|tls] packages as well as the ca-bundle and ca-certificates packages.
# wget http://downloads.openwrt.org/releases/19.07.5/targets/ramips/mt7621/openwrt-19.07.5-ramips-mt7621-ubnt-erx-squashfs-sysupgrade.bin
Downloading 'http://downloads.openwrt.org/releases/19.07.5/targets/ramips/mt7621/openwrt-19.07.5-ramips-mt7621-ubnt-erx-squashfs-sysupgrade.bin'
Connecting to 168.119.138.211:80
Failed to redirect to /releases/19.07.5/targets/ramips/mt7621/openwrt-19.07.5-ramips-mt7621-ubnt-erx-squashfs-sysupgrade.bin on downloads.openwrt.org
But in the fact, if you use or indicate to use wget, the user cant download firmware nor checksum files!
Yes.
(Personally, I prefer to install curl.)
It seems to me that readers should be warned of the necessity to install the lib in question or to use another tool, such as curl!
because in the state, they won't be able to download neither the firmware nor anything else....