January 6th, 2011

Quick Tip: Build numbers from Mercurial

All of my applications these days are versioned after the revision number of the version control repository they're built from. Normally, having a version number different from the human readable version number isn't necessary, but it's handy in some cases, such as distributing beta builds and managing multiple builds of the same version.

For example, to the left you can see Clarus version 1.5.4 (239), which is the version you can download from my website. The version submitted to the Mac App Store is 1.5.4 (247) for a couple of reasons:

  • If you're distributing apps both in and out of the App Store, you want the human-readable version number to be the same in both so users don't feel the version in the App Store (or not) is "newer" than their version.
  • It's handy for easily identifying App Store copies of your app with a simple "What version do you have?" question, just in case the App Store build has a unique issue.
  • The only changes between the builds are App Store related - no functionality changes at all.

This build number is inserted into the CFBundleVersion key in the application's Info.plist automatically by a build script. It's based on a script by Martin Pilkington that does a similar thing for the Bazaar VCS, but with a few differences:

  • It uses Mercurial rather than Bazaar.
  • It doesn't use the presence of a .hg directory to determine whether the project is under version control or not, since this breaks if your Xcode project isn't at the root level of the repository.

And, most importantly in my eyes:

  • It modifies the Info.plist file inside the built application rather than the one in your project. This minor difference means you don't get an unclean repository by building the application.

To use the script, right-click your Target in Xcode and choose Add > New Build Phase > New Run Script Build Phase. Set the new script to use the /usr/bin/perl shell, and paste in the script below. Enjoy!

#Check if we're versioned under hg
my $revno = `/usr/local/bin/hg id -n`;

if ($revno && $revno !~ m/abort/i) {

	print("Revision number is " . $revno);

    #get the revno minus the new line
    $revno =~ tr/+//d;
    substr($revno, -1, 1, "");
    #open the info plist
    open(my $input,  "< ",  "$ENV{BUILT_PRODUCTS_DIR}/$ENV{INFOPLIST_PATH}")  or die "Can't open Info.plist: $!";
    my $outputstring = "";
    #loop through each line until we find CFBundleVersion, then substitute the next line
    while (+<$input>) {
        $outputstring .= "$_";
        if (/[\t ]+<key>CFBundleVersion< \/key>\n/) {
            my $line = +< $input>;
            $line =~ s/([\t ]+<string>)(.*?)(< \/string>)/$1.($revno).$3/eg;
            $outputstring .= $line;
    #write back out to Info.plist
    open(my $output,  ">",  "$ENV{BUILT_PRODUCTS_DIR}/$ENV{INFOPLIST_PATH}")  or die "Can't open Info.plist: $!";
    print $output $outputstring;
} else {
    print "This project is not versioned";