Some friends cannot install Apple developer tools command line tools，When installing, it will prompt "The software cannot be installed.，Because it is currently unavailable from the software update server"，Let me teach you how to install it manually。 What are command line tools? Command Line Tools is a small standalone package from Apple，Available for macOS，Expanded the terminal with additional functionality。including but not limited to：svn、git、make、GCC、clang、perl、size、strip、strings、libtool、cpp、what、codesign and others...