Module sysvar

Access to special accounts with dynamically-updated data.

Sysvars are special accounts that contain dynamically-updated data about the network cluster, the blockchain history, and the executing transaction. Each sysvar is defined in its own submodule within this module. The clock, epoch_schedule, instructions, and rent sysvars are most useful to on-chain programs.

Simple sysvars implement the Sysvar::get method, which loads a sysvar directly from the runtime, as in this example that logs the clock sysvar:

use solana_program::{
    account_info::AccountInfo,
    clock,
    entrypoint::ProgramResult,
    msg,
    pubkey::Pubkey,
    sysvar::Sysvar,
};

fn process_instruction(
    program_id: &Pubkey,
    accounts: &[AccountInfo],
    instruction_data: &[u8],
) -> ProgramResult {
    let clock = clock::Clock::get()?;
    msg!("clock: {:#?}", clock);
    Ok(())
}

Since Solana sysvars are accounts, if the AccountInfo is provided to the program, then the program can deserialize the sysvar with Sysvar::from_account_info to access its data, as in this example that again logs the clock sysvar.

use solana_program::{
    account_info::{next_account_info, AccountInfo},
    clock,
    entrypoint::ProgramResult,
    msg,
    pubkey::Pubkey,
    sysvar::Sysvar,
};

fn process_instruction(
    program_id: &Pubkey,
    accounts: &[AccountInfo],
    instruction_data: &[u8],
) -> ProgramResult {
    let account_info_iter = &mut accounts.iter();
    let clock_account = next_account_info(account_info_iter)?;
    let clock = clock::Clock::from_account_info(&clock_account)?;
    msg!("clock: {:#?}", clock);
    Ok(())
}

When possible, programs should prefer to call Sysvar::get instead of deserializing with Sysvar::from_account_info, as the latter imposes extra overhead of deserialization while also requiring the sysvar account address be passed to the program, wasting the limited space available to transactions. Deserializing sysvars that can instead be retrieved with Sysvar::get should be only be considered for compatibility with older programs that pass around sysvar accounts.

Some sysvars are too large to deserialize within a program, and Sysvar::from_account_info returns an error, or the serialization attempt will exhaust the program’s compute budget. Some sysvars do not implement Sysvar::get and return an error. Some sysvars have custom deserializers that do not implement the Sysvar trait. These cases are documented in the modules for individual sysvars.

All sysvar accounts are owned by the account identified by sysvar::ID.

For more details see the Solana documentation on sysvars.

Re-exports

pub use sysvar_ids::ALL_IDS;Deprecated

pub use sysvar_ids::ALL_IDS;Deprecated

Modules

clock

Information about the network’s clock, ticks, slots, etc.

epoch_rewards

Epoch rewards for current epoch

epoch_schedule

Information about epoch duration.

fees

Current cluster fees.

instructions

The serialized instructions of the current transaction.

last_restart_slot

Information about the last restart slot (hard fork).

recent_blockhashes

Information about recent blocks and their fee calculators.

rent

Configuration for network rent.

rewards

This sysvar is deprecated and unused.

slot_hashes

The most recent hashes of a slot’s parent banks.

slot_history

A bitvector of slots present over the last epoch.

stake_history

History of stake activations and de-activations.

Macros

declare_deprecated_sysvar_id

Same as declare_sysvar_id except that it reports that this ID has been deprecated.

declare_sysvar_id

Declares an ID that implements SysvarId.

Structs

ALL_IDSDeprecated

Constants

ID

The const program ID.

Traits

Sysvar

A type that holds sysvar data.

SysvarId

A type that holds sysvar data and has an associated sysvar Pubkey.

Functions

check_id

Returns true if given pubkey is the program ID.

id

Returns the program ID.

is_sysvar_idDeprecated

Returns true of the given Pubkey is a sysvar account.