curl to Rust

What this tool is used for

• Converting an API's curl example into reqwest for a Rust service.
• Reproducing a captured request inside an existing Rust client.
• Getting the builder chain and body type right.
• Choosing between the async and blocking reqwest APIs.
• Producing a snippet for a small command-line tool.

Frequently Asked Questions

Do I need the blocking or the async reqwest?

reqwest is async-first and needs a runtime such as tokio. If you just want a script, enable the "blocking" feature and use reqwest::blocking::Client, which runs its own runtime internally. Do not call the blocking API from inside an async context — it panics.

Which Cargo features do I need?

JSON support is behind the "json" feature, so serde_json integration and .json() are unavailable without it. TLS comes from default-tls (native-tls); switch to rustls-tls for a pure-Rust stack that cross-compiles cleanly.

How do I handle the response?

Everything returns Result, so you propagate with ? and handle the error. Note that a 404 is Ok — call .error_for_status() to turn a non-2xx status into an Err, which is the closest equivalent to curl --fail.

How does curl's -k translate?

Client::builder().danger_accept_invalid_certs(true). The danger_ prefix is deliberate: it is in the API name so it shows up in review. Prefer .add_root_certificate() with your own CA where possible.

Should I build a new Client per request?

No. Client holds the connection pool and is designed to be created once and cloned — clone is cheap because it is internally reference-counted. Constructing one per call throws away pooling and TLS session reuse.

Which TLS backend is used?

reqwest defaults to native-tls, which uses the platform's own store, but `rustls-tls` is a pure-Rust alternative that cross-compiles cleanly and avoids linking OpenSSL. That choice is the usual cause of a build failing on one machine and not another.

How are errors handled idiomatically?

Each call returns a `Result`, so the `?` operator propagates failures up to a function returning `Result<_, reqwest::Error>` or a boxed error. Note that a 4xx or 5xx is not an error — call `error_for_status()` to turn it into one.

Common errors and gotchas

• Using the async API without a runtime, which compiles and then does nothing at run time.
• Mixing the blocking client into an async context, which panics rather than blocking.
• Forgetting the `json` feature flag, without which the `.json()` helpers do not exist.
• Assuming a non-2xx is an `Err`, when only a transport failure is — check `status()`.
• Creating a client per request rather than cloning one, which rebuilds the TLS setup each time.