Passing program arguments through Cargo

Question

I have some sample code that is currently making use of getopts which is specified as a dependency in Cargo.toml

[dependencies]
getopts = "0.2"

However I can not seem to pass argument ( -t , --test ) through Cargo (eg cargo run --test ) for obvious reasons.

Since I have specified that external dependency, trying to run rustc src/main.rs --test won't work either:

src/main.rs:2:5: 2:21 error: unresolved import `getopts::Options`. There is no `Options` in `getopts`
src/main.rs:2 use getopts::Options;
              ^~~~~~~~~~~~~~~~
error: aborting due to previous error

Is there another way to achieve this or some common alternative for the time being?

Answer 1

You can pass trailing arguments to cargo run using -- :

cargo run -- --test

From the man page:

All of the trailing arguments are passed to the binary to run. If you're passing arguments to both Cargo and the binary, the ones after -- go to the binary, the ones before go to Cargo.

Answer 2

It looks to me like you had two different problems. First is, how to pass flags to your executable (this was solved by @TartanLlama), the second is your compile error.

For future reference (this is at least true for my system with rust 1.19, cargo 0.20): You used an external crate getopts , which rustc by default does not know. cargo on the other hand understands that. By running cargo rustc (or even better cargo build ) instead of rustc the compile error will vanish.