mini-log

A tiny Rust logging crate controlled by the LOG_LEVEL environment variable.

Logging is disabled by default.

Install

Add the crate to your project:

cargo add mini-log

Usage

use mini_log::*;

fn main() {
    LogMessage::new(Level::Warning, "My Message here");
}

By default, this prints nothing.

To enable output, set the LOG_LEVEL environment variable.

LOG_LEVEL=WARNING cargo run

Example output:

[2026-05-30 - 09:30:42:10] - WARNING - My Message here

Log levels

LOG_LEVEL=DEBUG    prints DEBUG, INFO, WARNING, ERROR
LOG_LEVEL=INFO     prints INFO, WARNING, ERROR
LOG_LEVEL=WARNING  prints WARNING, ERROR
LOG_LEVEL=WARN     prints WARNING, ERROR
LOG_LEVEL=ERROR    prints ERROR only
LOG_LEVEL=OFF      prints nothing

Example if LOG_LEVEL is missing or invalid:

mini-log: LOG_LEVEL is not set, no logs will be printed.
Set one of these environment variable:
    LOG_LEVEL=DEBUG
    LOG_LEVEL=INFO
    LOG_LEVEL=WARNING
    LOG_LEVEL=ERROR
    LOG_LEVEL=OFF

Windows

Powershell:

$env:LOG_LEVEL="WARNING"
cargo run

cmd.exe

set LOG_LEVEL=WARNING
cargo run

macOS / Linux:

LOG_LEVEL=WARNING cargo run

Only this will be printed:

[2026-05-30 - 09:30:42:10] - WARNING - Warning message
[2026-05-30 - 09:30:42:10] - ERROR - Error message

Time format

By default, mini-log uses 24h timestamp format:

2026-05-30 - 09:30:42:10 (YYYY-MM-dd - hour:minute:second:millisecond)

The full log output looks like this:

[2026-05-30 - 09:30:42:10] - WARNING - My Message here

The timestamp format can be changed with the LOG_TIME_FORMAT environment variable.

Supported values:

LOG_TIME_FORMAT=DEFAULT    2026-05-30 - 09:30:42:10
LOG_TIME_FORMAT=RFC3339    2026-05-30T09:30:42.100+02:00
LOG_TIME_FORMAT=TIME_ONLY  09:30:42
LOG_TIME_FORMAT=DATE_ONLY  2026-05-30
LOG_TIME_FORMAT=UNIX       1780126242

Example:

LOG_LEVEL=WARNING LOG_TIME_FORMAT=RFC3339 cargo run

Example output:

[2026-05-30T09:30:42.100+02:00] - WARNING - My Message here

If LOG_TIME_FORMAT is missing or invalid, mini-log uses the default timestamp format.

Examples

use mini_log::*;

fn main() {
    LogMessage::new(Level::Debug, "Debug message");
    LogMessage::new(Level::Info, "Info message");
    LogMessage::new(Level::Warning, "Warning message");
    LogMessage::new(Level::Error, "Error message");
}

use mini_log::*;

fn main() {
    if is_enabled(Level::Debug) {
        println!("Debug logging is currently enabled");
    }

    LogMessage::new(Level::Warning, "My Message here");
}

Notes

mini-log writes to stdout using println!.

It is intentionally small and simple.