What is a Rust binary library?

A "Rust binary library" is not a standard term within the Rust programming language ecosystem. Typically, in Rust, we differentiate between two primary types of crates (Rust's unit of code organization): binary crates and library crates.

Let's clarify what each type represents:

1. Binary Crates:

- These are crates that produce an executable binary file. This means they contain a main function, which is the entry point of the program. When compiled, binary crates result in a standalone application that can be run directly. Examples include command-line tools, server applications, and graphical user interfaces.

- You define a binary crate using the [package] section in a Cargo.toml file (the manifest file for Rust projects), along with the src/main.rs file.

2. Library Crates:

- These crates are intended to be used as dependencies by other crates. They do not contain a main function and, thus, cannot be directly executed. Library crates typically provide functions, structures, and other types that can be reused across multiple projects. They are the building blocks for applications.

- You define a library crate using the [package] section and the src/lib.rs file, which is the entry point for the library's code.

Given these definitions, the term "Rust binary library" is a bit of a misnomer because binaries and libraries are generally mutually exclusive. However, one could be interpreted in a few contexts:

Possible interpretations of "Rust binary library":

- A library used by a binary: This is likely what is being referred to. It means you have a library crate (.rs file in src/lib.rs ) that's used as a dependency within a binary crate (.rs file in src/main.rs ).

- A compiled library: If someone refers to a library as being "binary," they might be indicating the library is compiled, i.e., it exists as a file with binary code that's consumable (or linked against) by another application, and not in its human-readable source code (.rs) form. This file could be in .rlib or .so format (depending on the platform).

- A binary using a library: It could also be that someone using this term means a binary executable, but one that leverages code organized in reusable library structures.

Therefore, when encountering "Rust binary library," understanding the context is vital. It's usually not a technical term, so it needs more context to understand its meaning.

Key takeaways:

- Rust has binary crates (executables) and library crates (reusable code).

- The term "Rust binary library" is non-standard, likely indicating a library being consumed by or compiled for a binary.

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