just sharing my experience for anyone experiencing same problem.
using windows10 64bit, and following rust book, in ch 09-01, when i follow the book's text, and try to use 'RUST_BACKTRACE=1', i get
''RUST_BACKTRACE' is not recognized as an internal or external command'.
searching the web revealed only a few answers, so i had to use good ol' 'trial&error' technique.
- type into cmd: 'set RUST_BACKTRACE=1', confirm with [enter]
- then type 'cargo run'
now it works as expected, output is similar to book's example.
to disable BACKTRACE:
- type into cmd: 'set RUST_BACKTRACE=0'
now 'cargo run' will output 'original' error messages.
s love nia