I tried installing bison and flex :
sudo pacman -Syu install bison flex
This is what I got:
:: Synchronizing package databases...
core is up to date
extra is up to date
community is up to date
multilib is up to date
error: target not found: install
warning: flex-2.6.4-2 is up to date -- reinstalling
sudo pacman -Syu install bison flex
There is not a package nor a sub-command named "install". To install/upgrade
packages, pacman -Syu is usually enough:
sudo pacman -Syu bison flex
From the "EXAMPLES" section in the pacman(8) man page:
pacman -Syu gpm
Update package list, upgrade all packages, and then install gpm if it wasn’t already installed.
See also Pacman#Installing_packages.