Function init_logger_from_env

Source

pub fn init_logger_from_env<P: AsRef<Path>>(
    file_path: Option<P>,
) -> Result<(), LogError>

Expand description

Initialize a logger from the RUST_LOG environment variable.

This reads the RUST_LOG environment variable to configure log levels and module-specific filters. If RUST_LOG is not set, defaults to Info level.

§Supported RUST_LOG formats

debug - Set default level to debug
my_crate=debug - Set specific module to debug
my_crate::module=trace - Set submodule to trace
my_crate=debug,other_crate::module=trace - Multiple module filters
warn - Set default level to warn

§Arguments

file_path - Optional path to a log file. If None, logs will only go to stdout.

§Returns

Ok(()) if initialization succeeded, or an error if it failed.

§Example

use fstdout_logger::init_logger_from_env;

// Set RUST_LOG=debug or RUST_LOG=my_crate=trace,other=warn
init_logger_from_env(Some("app.log"))
    .expect("Failed to initialize logger");

Examples found in repository ?

examples/module_filters.rs (line 69)

67fn main() {
68    // Initialize logger from RUST_LOG environment variable
69    if let Err(e) = init_logger_from_env(Some("module_filters.log")) {
70        eprintln!("Failed to initialize logger: {e}");
71        return;
72    }
73
74    println!("=== Module Filters Example ===");
75    println!("Current RUST_LOG: {:?}", std::env::var("RUST_LOG").unwrap_or_else(|_| "not set".to_string()));
76    println!("\nTry running with different RUST_LOG values:");
77    println!("  RUST_LOG=debug cargo run --example module_filters");
78    println!("  RUST_LOG=trace cargo run --example module_filters");
79    println!("  RUST_LOG=module_filters::network=trace,warn cargo run --example module_filters");
80    println!("  RUST_LOG=module_filters::database=error cargo run --example module_filters");
81    println!("\n--- Application Logs ---\n");
82
83    // Main application logs
84    info!("Application starting...");
85    debug!("Debug mode enabled");
86    trace!("This is a trace message from main");
87
88    // Network module operations
89    info!("Testing network module:");
90    network::connect();
91    network::send_data();
92
93    // Database module operations
94    info!("\nTesting database module:");
95    database::query();
96    database::transaction();
97
98    // Cache module operations
99    info!("\nTesting cache module:");
100    cache::get("user:123");
101    cache::set("user:123");
102
103    // More main application logs
104    warn!("This is a warning from main");
105    error!("This is an error from main");
106
107    info!("\nApplication finished");
108    println!("\n--- End of Logs ---");
109    println!("\nCheck 'module_filters.log' for complete log output.");
110}

init_logger_from_env