It seems like you copied and pasted parts of your command resulting to non ASCII characters.
In particular, the dash (-
) seems to be the issue here. Try again with this:
gem install --http-proxy http://web-proxy:8088 rails -v '3.2.18' --no-rdoc --no-ri
The error message partly gives it away (at least it points to encoding issues) in Could not find a valid gem 'ûv' (>= 0)
.