Overview

zlog is an application-level logging library that provides some APIs to write logging message to an output file.

My inspiration came from using Google's glog library, writing some cool applications with the ability to log actions easily.

So credits go to Google.

This code was also taken from my zigwm project, which needed logging to figure out what was going on.

Tip

Like Glog, this library is also thread-safe

Getting Started

You can install the library by running

zig fetch --save git+https://github.com/isaac-westaway/zlog

Then add the dependency in your build.zig file

const zlog = b.dependency("zlog", .{ .target = target, .optimize = optimize });
exe.root_module.addImport("zlog", zlog.module("zlog"));

Usage

Quickstart

You can get started by initializing the logging file:

pub fn main() !void {
    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
    defer std.debug.assert(gpa.deinit() == .ok);
    var allocator = gpa.allocator();

    try Logger.initializeLogging(&allocator, 
        .{ .absolute_path = "/home/isaacwestaway/Documents/zig/zlog/", .file_name = "log" },
        .{ .severity = .info }
    );
    defer Logger.Log.close();
}

And then log a message to the logfile:

...
var Log = Logger.Log;

const str: []const u8 = "world";
const timestamp: i64 = std.time.timestamp();

const current_time: []const u8 = Logger.timestampToDatetime(allocator, timestamp);
defer allocator.free(current_time);

try Log.info("MAIN", "Hello, {s}", .{ str });
try Log.warn("MAIN", "Current Timestamp: {d}", .{ timestamp} );
try Log.err("MAIN", "Hello {s}, at {s}", .{ str, current_time });

// Will crash the program upon logging!
try Logger.Log.fatal("MAIN", "I am Crashing Now!", .{});

Output:

INFO-MAIN-2024/9/17-0:31:57-T250650:Hello, world
WARN-MAIN-2024/9/17-0:31:57-T250650:Current Timestamp: 1726533117
ERROR-MAIN-2024/9/17-0:31:57-T250650:Hello world, at 2024/9/17-0:31:57
FATAL-MAIN-2024/9/17-0:31:57-T250650:I am Crashing Now!

Using a custom prefix

// The callback must have these two arguments
fn testLogPrefix(allocator: *std.mem.Allocator, log_level: []const u8) []const u8 {
    const current_time = Logger.timestampToDatetime(allocator.*, std.time.timestamp());
    const str: []u8 = std.fmt.allocPrint(allocator.*, "{s}: Some Extra Messages!, such as the time: {s}: ", .{ log_level, current_time }) catch {
        return undefined;
    };
    return str;
}

pub fn main() !void {

    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
    defer std.debug.assert(gpa.deinit() == .ok);
    var allocator = gpa.allocator();

    try Logger.initializeLogging(&allocator, 
        .{ .absolute_path = "/home/isaacwestaway/Documents/zig/zlog/", .file_name = "log" }, 
        .{ .severity = .info }
    );
    try Logger.installLogPrefix(&testLogPrefix);
    defer Logger.Log.close();

    var Log = Logger.Log;

    const str: []const u8 = "world";
    const timestamp: i64 = std.time.timestamp();

    const current_time: []const u8 = Logger.timestampToDatetime(allocator, timestamp);
    defer allocator.free(current_time);

    try Log.info("MAIN", "Hello, {s}", .{str});
    try Log.warn("MAIN", "Current Timestamp: {d}", .{timestamp});
    try Log.err("MAIN", "Hello {s}, at {s}", .{ str, current_time });

    // Will crash the program upon logging!
    try Logger.Log.fatal("MAIN", "I am Crashing Now!", .{});
}

Output:

INFO: Some Extra Messages!, such as the time: 2024/9/17-0:32:51: Hello, world
WARN: Some Extra Messages!, such as the time: 2024/9/17-0:32:51: Current Timestamp: 1726533171
ERROR: Some Extra Messages!, such as the time: 2024/9/17-0:32:51: Hello world, at 2024/9/17-0:32:51
FATAL: Some Extra Messages!, such as the time: 2024/9/17-0:32:51: I am Crashing Now!

Todo

• Some better test cases