Which libc is that?

For Linux, it can be fun to figure out which libc version your apps are bound to.  After a bit of digging, I found that you can actually run the libc.so as a *binary* - which outputs its own version info.  This will work on all the linuxes, without resorting to asking a package management tool:

 ldd /bin/sh |grep libc.so | awk '{print $3}' | sh