# subxt The [`subxt`](https://github.com/paritytech/subxt) library enables you to submit transactions to a Substrate node through remote procedure calls. Before you use the `subxt` library, you can use the standalone `subxt` command-line interface to download the metadata for the Substrate node you want to use as the target for submitting transactions. The `subxt-cli` tool enables you to perform two key tasks that are critical to using the `subxt` library: * You can use the `subxt-cli` tool to download the metadata from any target Substrate node. * You can use the `subxt-cli` tool to generate the runtime API code from the metadata from any target Substrate node. You can use the `subxt` library and `subxt-cli` tool for any node that uses metadata v14 and later. For examples of how to use the `subxt` library, see the [examples](https://github.com/paritytech/subxt/tree/master/examples) folder. ### Installation To install `subxt-cli`: 1. Open a terminal shell, if necessary. 2. Verify that you have the Rust compiler and toolchain, if necessary. 3. Download the required packages with the following command: `cargo install subxt-cli` ### Basic command usage The basic syntax for running `subxt` commands is: `subxt ` To use the commands exposed by `subxt`, you must either be running a node locally or specify the chain you're targeting. If the metadata is already provided, it is possible to use the `codegen` subcommand without running a node. #### Flags You can use the following optional flags with the `subxt` command. | Flag | Description | | ------------- | ----------------------------- | | -h, --help | Displays usage information. | | -V, --version | Displays version information. | #### Subcommands You can use the following subcommands with the `subxt` command-line interface. | Command | Description | | ---------- | ---------------------------------------------------------------------- | | `codegen` | Generates runtime API client code from metadata. | | `metadata` | Downloads metadata from a Substrate node for use with `subxt` codegen. | #### Output Depending on how you specify the subcommand, the output from `subxt` displays some or all of the following information: | This field | Contains | | ---------- | ------------------------------------------- | | Metadata | A file with the metadata of a target chain. | | API | A file with the API of the target chain. | #### Examples To display version information for the `subxt` program, run the following command: `subxt --version` To display usage information for the `subxt metadata` command, run the following command: `subxt metadata --help` ### codegen Use the `subxt codegen` command to generate an interface for some target Substrate node. This could be useful for debugging or modifying a node's API to meet certain hardware constraints. **Basic usage** `subxt codegen [OPTIONS]` **Flags** You can use the following optional flags with the `subxt codegen` command. | Flag | Description | | --------------- | --------------------------- | | `-h, --help` | Displays usage information. | | `-V, --version` | Prints version information. | **Options** You can use the following command-line options with the `subxt codegen` command. | Option | Description | | ------------------- | -------------------------------------------------------------------------- | | `-f, --file ` | Specifies the path to the encoded metadata file. | | `--url ` | Specifies the URL of the Substrate node to query for metadata for codegen. | **Examples** To format the generated API and print it to the terminal, run the following command: `subxt codegen | rustfmt` To save the generated API in a file, run the following command: `subxt codegen | rustfmt --edition=2018 > api.rs` ### metadata Use the `subxt metadata` command to get the metadata of the target Substrate node. **Basic usage** `subxt metadata [OPTIONS]` **Flags** You can use the following optional flags with the `subxt metadata` command. | Flag | Description | | --------------- | --------------------------- | | `-h, --help` | Displays usage information. | | `-V, --version` | Prints version information. | **Options** You can use the following command-line options with the `subxt metadata` command. | Option | Description | | ----------------------- | -------------------------------------------------------------------------------------------------------------------------- | | `-f, --format ` | Specifies the format of the metadata to display. Valid formats are `json`, `hex` or `bytes`. The default format is `json`. | | `--url ` | Specifies the URL of the Substrate node to query for metadata. The default URL is `http://localhost:9933`. | **Examples** To save the metadata from the local node encoded in bytes to a file, run the following command: `subxt metadata -f bytes > metadata.scale` To save the metadata from the Rococo network to a JSON file, run the following command: `subxt metadata --url https://rococo-rpc.polkadot.io:443 > .json` To query type `125` from the array of types in the metadata and output in JSON, run the following command: `subxt metadata --format json | jq '.[1].V14.types.types | .[125]'` --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. 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