Haxe Code Cookbook
Haxe programming cookbookMacrosAdd git commit-hash in build

Add git commit-hash in build

Reading time: 1 minute

This example executes a process on the system, compile-time. This allows to run a git command git rev-parse HEAD and use its result as the value.

class Version {
  public static macro function getGitCommitHash():haxe.macro.Expr.ExprOf<String> {
    #if !display
    var process = new sys.io.Process('git', ['rev-parse', 'HEAD']);
    if (process.exitCode() != 0) {
      var message = process.stderr.readAll().toString();
      var pos = haxe.macro.Context.currentPos();
      haxe.macro.Context.error("Cannot execute `git rev-parse HEAD`. " + message, pos);
    // read the output of the process
    var commitHash:String = process.stdout.readLine();
    // Generates a string expression
    return macro $v{commitHash};
    // `#if display` is used for code completion. In this case returning an
    // empty string is good enough; We don't want to call git on every hint.
    var commitHash:String = "";
    return macro $v{commitHash};


The function can be called like any other static function in Haxe.

// use as field
@:keep public static var COMMIT_HASH(default, never):String = Version.getGitCommitHash();

// ..or trace to output

sys.io.Process API documentation

Allan Dowdeswell
Mark Knol
Last modified:
Category:  Macros