Formatted Logging

This example demonstrates how to use the formatted logging methods (infof, debugf, etc.) to log messages with arguments, similar to printf or std.log. This allows for dynamic message construction without manual string concatenation. All formatted output supports colors based on log level.

Code Example

const std = @import("std");
const logly = @import("logly");

pub fn main() !void {
    // Enable ANSI colors on Windows
    _ = logly.Terminal.enableAnsiColors();

    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
    defer _ = gpa.deinit();
    const allocator = gpa.allocator();

    const logger = try logly.Logger.init(allocator);
    defer logger.deinit();

    // 1. Formatted Logging with Colors
    // Use methods ending with 'f' to pass format strings and arguments
    // Each line will be colored based on log level
    // Pass @src() for clickable file:line output
    try logger.infof("User {s} logged in with ID {d}", .{ "Alice", 12345 }, @src());
    try logger.warningf("Disk usage is at {d}%", .{ 85 }, @src());
    try logger.warnf("Short alias: {d}% disk used", .{ 85 }, @src());  // warnf alias
    try logger.errf("Failed to connect to {s}:{d}", .{ "localhost", 8080 }, @src());
    try logger.critf("System critical: {s}", .{ "out of memory" }, @src());  // critf alias

    // 2. Scoped Formatted Logging
    // Scoped loggers also support formatted methods with colors
    const db_logger = logger.scoped("database");
    try db_logger.debugf("Query executed in {d}ms: {s}", .{ 15, "SELECT * FROM users" }, @src());
    try db_logger.infof("Connected to database '{s}'", .{ "production_db" }, @src());

    // 3. Custom Level Formatted Logging with Custom Colors
    try logger.addCustomLevel("AUDIT", 22, "35"); // Magenta
    try logger.customf("AUDIT", "User {s} performed action: {s}", .{ "Bob", "DELETE" }, @src());

    // 4. Mixing styles
    // You can mix standard string logging with formatted logging
    try logger.info("Standard message", @src());
    try logger.infof("Formatted message with {s}", .{ "arguments" }, @src());
}

Expected Output

All output is colored based on log level (entire line):

[INFO] User Alice logged in with ID 12345       (white)
[WARNING] Disk usage is at 85%                  (yellow)
[ERROR] Failed to connect to localhost:8080     (red)
[database] [DEBUG] Query executed in 15ms...    (blue)
[database] [INFO] Connected to database...      (white)
[AUDIT] User Bob performed action: DELETE       (magenta - custom)
[INFO] Standard message                         (white)
[INFO] Formatted message with arguments         (white)

Custom Format Strings with Colors

You can also use custom format strings with colors:

var config = logly.Config.default();
config.log_format = "{time} | {level} | {message}";
config.color = true;  // Colors apply to entire formatted line
logger.configure(config);

try logger.info("Application started");
try logger.warning("High memory usage");
try logger.err("Connection failed");

Output (each line colored by level):

2024-01-15 10:30:45 | INFO | Application started      (white)
2024-01-15 10:30:45 | WARNING | High memory usage     (yellow)
2024-01-15 10:30:45 | ERROR | Connection failed       (red)