# tracing::trace - Rust
API documentation for the Rust `trace` macro in crate `tracing`.
Keywords: rust, rustlang, rust-lang, trace

# Macro tracing::trace [−] [src]

    macro_rules! trace {
        (target: $target:expr, parent: $parent:expr, { $($field:tt)* }, $($arg:tt)* ) => { ... };
        (target: $target:expr, parent: $parent:expr, $($k:ident).+ $($field:tt)+ ) => { ... };
        (target: $target:expr, parent: $parent:expr, ?$($k:ident).+ $($field:tt)+ ) => { ... };
        (target: $target:expr, parent: $parent:expr, %$($k:ident).+ $($field:tt)+ ) => { ... };
        (target: $target:expr, parent: $parent:expr, $($arg:tt)+ ) => { ... };
        (parent: $parent:expr, { $($field:tt)+ }, $($arg:tt)+ ) => { ... };
        (parent: $parent:expr, $($k:ident).+ = $($field:tt)*) => { ... };
        (parent: $parent:expr, ?$($k:ident).+ = $($field:tt)*) => { ... };
        (parent: $parent:expr, %$($k:ident).+ = $($field:tt)*) => { ... };
        (parent: $parent:expr, $($k:ident).+, $($field:tt)*) => { ... };
        (parent: $parent:expr, ?$($k:ident).+, $($field:tt)*) => { ... };
        (parent: $parent:expr, %$($k:ident).+, $($field:tt)*) => { ... };
        (parent: $parent:expr, $($arg:tt)+) => { ... };
        (target: $target:expr, { $($field:tt)* }, $($arg:tt)* ) => { ... };
        (target: $target:expr, $($k:ident).+ $($field:tt)* ) => { ... };
        (target: $target:expr, ?$($k:ident).+ $($field:tt)* ) => { ... };
        (target: $target:expr, %$($k:ident).+ $($field:tt)* ) => { ... };
        (target: $target:expr, $($arg:tt)+ ) => { ... };
        ({ $($field:tt)+ }, $($arg:tt)+ ) => { ... };
        ($($k:ident).+ = $($field:tt)*) => { ... };
        ($($k:ident).+, $($field:tt)*) => { ... };
        (?$($k:ident).+, $($field:tt)*) => { ... };
        (%$($k:ident).+, $($field:tt)*) => { ... };
        (?$($k:ident).+) => { ... };
        (%$($k:ident).+) => { ... };
        ($($k:ident).+) => { ... };
        ($($arg:tt)+) => { ... };
    }

Constructs an event at the trace level.

This functions similarly to the `event!` macro. See the top-level documentation for details on the syntax accepted by this macro.

# Examples

    use tracing::trace;
    let pos = Position { x: 3.234, y: -1.223 };
    let origin_dist = pos.dist(Position::ORIGIN);

    trace!(position = ?pos, ?origin_dist);
    trace!(
        target: "app_events",
        position = ?pos,
        "x is {} and y is {}",
        if pos.x >= 0.0 { "positive" } else { "negative" },
        if pos.y >= 0.0 { "positive" } else { "negative" }
    );