Output format: minimal

The purpose of the minimal output format option is to provide just enough output for a machine (or shell script!) to be understandable, while not requiring elaborate parsers like the json output format. It may also be used as a minimal human-readable format.

This output format can be summarized by the following two statements:

If the command was successful, it prints the commands final result and exits with a zero exit code. Output is printed to stdout.
If the command was unsuccessful, it prints an error message, and exits with a non-zero exit code. Output is printed
to stderr.

You may also refer to the 🚧 TODO 🚧 section to determine which kind of errors result in a non-zero exit code, and how different errors are categorised.

Output by subcommand

# cargo msrv (find)

If the MSRV was found, we report this minimal supported Rust version by writing it to stdout. If it could not be found, we report none instead, and write this value to stderr.

Example 1

If the MSRV is 1.60.0, the output will be just 1.60.0.

$ cargo msrv find --output-format minimal
# stdout
1.60.0

Example 2

If the MSRV can't be found, for example if your project requires a nightly compiler feature or has incorrect syntax, the output will be none.

$ cargo msrv find --output-format minimal
# stderr
none

# cargo msrv list

The list subcommand is not supported by the minimal output format, and "unsupported" will be printed. Support may be added in the future.

# cargo msrv set

The set subcommand prints the version set as MSRV.

Example 1

If we set our MSRV to be 1.31, the output will be 1.31.

cargo msrv find --output-format minimal set 1.31
# stdout
1.31

# cargo msrv show

The show subcommand prints the detected MSRV, if specified in the Cargo Manifest.

Example 1

Assuming our Cargo manifest contains a 1.60 MSRV, cargo-msrv will print 1.60.

Cargo.toml

[package]
rust-version = "1.60"

Shell

$ cargo msrv find --output-format minimal show
# stdout
1.60

Example 2

Assuming our Cargo manifest lists the MSRV in the package.metadata.msrv field, cargo-msrv will print 1.21.0. The package.rust-version field has precedence over the package.metadata.msrv. You may see the package.metadata.msrv key for crates which use a Cargo version which does not yet support the package.rust-version field. cargo-msrv supports both fields.

Cargo.toml

[package.metadata]
msrv = "1.21.0"

Shell

$ cargo msrv find --output-format minimal show
# stdout
1.21.0

# cargo msrv verify

The verify subcommand prints true (to stdout) with exit code zero if checking the toolchain for this platform which matches the MSRV succeeds. Else, it prints false (to stderr) with an exit code which is non-zero.

Example 1

Assuming our Cargo manifest contains an MSRV definition in the package.rust-version or package.metadata.msrv field, and the compatibility check succeeds:

[package.metadata]
msrv = "1.31"

Shell

$ cargo msrv find --output-format minimal verify
# stdout
true

Example 2

Assuming the given crate is incompatibility with the given MSRV:

Shell

$ cargo msrv find --output-format minimal verify --rust-version 1.31
# stderr
false

The cargo-msrv Book 🦀