Interactive REPL

The ethrex REPL is an interactive Read-Eval-Print Loop for Ethereum JSON-RPC. It lets you query any Ethereum node directly from your terminal using a concise namespace.method syntax.

Quick Start

# Via the ethrex binary
ethrex repl

# Connect to a specific endpoint
ethrex repl -e https://eth.llamarpc.com

# Execute a single command and exit
ethrex repl -x "eth.blockNumber"

CLI Options

ethrex repl [OPTIONS]

Options:
  -e, --endpoint <URL>       JSON-RPC endpoint [default: http://localhost:8545]
      --history-file <PATH>  Path to command history file [default: ~/.ethrex/history]
  -x, --execute <COMMAND>    Execute a single command and exit

RPC Commands

Type namespace.method with arguments separated by spaces or in parentheses:

> eth.blockNumber
68943

> eth.getBalance 0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045
1000000000000000000

> eth.getBalance("0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045", "latest")
1000000000000000000

> eth.getBlockByNumber 100 true
┌─────────────────────────────────────────┐
│            number   100                 │
│         timestamp   1438270128          │
│  ...                                    │
└─────────────────────────────────────────┘

Supported Namespaces

Namespace	Methods	Description
`eth`	30	Accounts, blocks, transactions, filters, gas, proofs
`debug`	8	Raw headers/blocks/transactions/receipts, tracing
`admin`	4	Node info, peers, log level, add peer
`net`	2	Network ID, peer count
`web3`	1	Client version
`txpool`	2	Transaction pool content and status

Type .help to list all namespaces, .help eth to list methods in a namespace, or .help eth.getBalance for detailed method documentation.

ENS Name Resolution

Any command that accepts an address also accepts ENS names:

> eth.getBalance vitalik.eth
Resolved vitalik.eth -> 0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045
1000000000000000000

Resolution is done on-chain by querying the ENS registry at 0x00000000000C2E074eC69A0dFb2997BA6C7d2e1e. This works against any endpoint connected to Ethereum mainnet.

Utility Functions

Function	Example	Description
`toWei`	`toWei 1.5 ether` → `1500000000000000000`	Convert to wei
`fromWei`	`fromWei 1000000000 gwei` → `1`	Convert from wei
`toHex`	`toHex 255` → `0xff`	Decimal to hex
`fromHex`	`fromHex 0xff` → `255`	Hex to decimal
`keccak256`	`keccak256 0x68656c6c6f` → `0x1c8a...`	Keccak-256 hash
`toChecksumAddress`	`toChecksumAddress 0xd8da...` → `0xd8dA...`	EIP-55 checksum
`isAddress`	`isAddress 0xd8dA...` → `true`	Validate address format

Units for toWei/fromWei: wei, gwei, ether (or eth).

Built-in Commands

Command	Description
`.help [namespace\|command]`	Show help
`.exit` / `.quit`	Exit the REPL
`.clear`	Clear the screen
`.connect <url>`	Show or change endpoint
`.history`	Show history file path

Other Features

Tab completion for namespaces, methods, block tags, and utilities
Parameter hints shown after typing a full method name
Multi-line input — unbalanced {} or [] automatically continues to the next line
Persistent history saved to ~/.ethrex/history
Formatted output — addresses, hashes, hex quantities, and nested objects are colored and auto-formatted

Using with ethrex dev mode

The REPL pairs well with ethrex dev mode. Start a local node, then connect the REPL to it:

# Terminal 1: start ethrex in dev mode
ethrex --dev

# Terminal 2: connect the REPL (default endpoint is localhost:8545)
ethrex repl

Running from source

# As an ethrex subcommand
cargo run -p ethrex -- repl

# Or directly
cargo run -p ethrex-repl

# Run tests
cargo test -p ethrex-repl

Keyboard shortcuts

Ethrex