What's the best way to rebuild the icudt51l.dat file in /usr/share/icu/? ICU (International Components for Unicode) is a set of C/C++ and Java libraries I think, that seem integral to OS X as built-in apps as well as apps using vital system services refuse to work properly or crash after this file got accidentally deleted. I'm attempting to retrieve it, but as this is on a system drive getting it back might not be possible.

  • reinstall OSX -or at least try the combo update – mmmmmm Jul 7 '15 at 16:31
  • Thanks, but there's no way I'd reinstall OS X for one file. – MiB Jul 7 '15 at 16:51
  • I would try to fish out this file from the OSX installer with something like Pacifist. – ccpizza Apr 26 '17 at 20:21

Another solution for this is to boot into your recovery partition with CMD+R while your machine is booting. From there you can open the Terminal from Utilities in the menu bar. Then you can copy the file with:

cp /usr/share/icu/icudt51l.dat /Volumes/YOUR_DRIVE/usr/share/icu

If your drive has FileVault enabled you may have to unlock that through disk utility first.

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  • 1
    That's certainly a viable solution if you do have a Recovery Partition and especially if you don't have net access when you need to fix this. While my compile solution worked for me, I think this may be the one most useful and readily available for anyone. – MiB Jul 23 '15 at 11:59

In Terminal with developer tools installed I ran the commands:

curl -O http://download.icu-project.org/files/icu4c/51.2/icu4c-51_2-src.tgz
tar xvf icu4c-51_2-src.tgz
cd icu/source
rm -rf data
./runConfigureICU MacOSX --with-data-packaging=archive

and from data/out I copied icudt51l.dat to /usr/share/icu/.

Apps now seem to run fine again, but it would seem some caches got deleted.

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Just reinstall Mac OS X 10.9.5 Combo Updater. The file "icudt51l.dat" is part of the update:

enter image description here

If you own/use Pacifist (AFAIK the free trial lasts for 30 days) you may spare the full update and just install the file to the proper path.

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  • Yes, that is a good suggestion. I started a download of the combo update but Firefox crashed before it got half-way multiple times (as did my recovery application). I then copied the download link and used curl instead. But my build was already finished so used that first. But now I used Pacifist to install this file to the default location. Great! – MiB Jul 7 '15 at 16:50
  • I also attempted to reinstall the whole 10.9.5 Combo update, but that's not possible. – MiB Jul 7 '15 at 18:30
  • @MiB Which error message do you get? – klanomath Jul 7 '15 at 18:32
  • klanomath, the installer just says my OS X 10.9.5 drive isn't eligible. – MiB Jul 9 '15 at 11:55

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