Simulate Execution

Run eth_call and eth_estimateGas for a manual call or existing transaction.

Use execution simulate to execute a call request locally against the selected block state.

The command does not submit a transaction. It calls eth_call for return data and eth_estimateGas for a gas estimate.

Manual Call

rex execution simulate \
  --to 0x0000000000000000000000000000000000000000 \
  --data 0x \
  --value 0

Simulate from a Transaction

You can convert an existing transaction into an eth_call request:

rex execution simulate \
  --tx 0xaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa \
  --block latest

This fetches the transaction with eth_getTransactionByHash, copies its call fields, and executes them through eth_call.

Example Output

EXECUTION SIMULATE

Source:       manual call
Block:        latest
From:         -
To:           0x0000000000000000000000000000000000000000
Value:        0 wei
Input bytes:  0
Output bytes: 0
Gas estimate: 21000

Return data:
  0x

Field Notes

• --block chooses the state context for eth_call and eth_estimateGas.
• --tx is a convenience for building the call request. It is not a historical transaction replay.
• Use Replay Tx when you need the actual call tree for a mined transaction.
• Use --full-output if the return data is long and you want the complete hex value.