Please note that through a change to the error handling of CURL in our build.sh script, this errors appears lately with the output as seen below:

[!] /bin/bash -c
set -e
sh build.sh cocoapods-setup

core is not a symlink. Deleting...
Downloading dependency: core 0.96.1
Downloading core failed:
curl: (56) SSLRead() return error -9806

Whenever the first download via CocoaPods has failed, the cache could be in a corrupt state. It might help in such cases to remove Realm from the CocoaPods cache, what can be achieved by running the following command:

rm -rf ~/Library/Caches/CocoaPods/Pods/**/Realm*

In addition, the integration in the project should be reset.

rm -rf /Pods

After that and ensuring that you've a working internet connection without restrictions, you can run the following:

pod install --verbose

I am in china and has the same problem when I use VPN. The core realm package is 63MB, that is so big and the VPN is hard to download it. By looking the build.sh of realm, it use getconf DARWIN_USER_TEMP_DIR1 to get the tmp direction and check the $TMPDIR, if it has the core-${REALM_CORE_VERSION}.tar.bz2. So I download the https://static.realm.io/downloads/core/realm-core-0.97.1.tar.bz2 by VPN and move it to $TMPDIR, then you can pod install.

1.cd `getconf DARWIN_USER_TEMP_DIR`
2.curl https://static.realm.io/downloads/core/realm-core-0.97.1.tar.bz2 -o realm-core-0.97.1.tar.bz2
(use VPN or use the website to help download on onedrive: http://ctrlq.org/save/)
3.cd ~/yourProjectDir/
4.pod install --verbose

@madawei2699 says the correct answer. I am also a developer in China.The solution is download realm-core-XXX.tar.bz2 and copy it into /tmp/ dir. So I suggested the maintainer to list the download url of each realm version.