Can someone explain about Linux library naming?

Question

When I create a library on Linux, I use this method:

1. Build: libhelloworld.so.1.0.0
2. Link: libhelloworld.so.1.0.0 libhelloworld.so
3. Link: libhellowo

Answer 1

From an old email I sent to a colleague about this question:

Let's look at libxml as an example. First of all, shared objects are stored in /usr/lib with a series of symlinks to represent the version of the library availiable:

lrwxrwxrwx 1 root root     16 Apr  4  2002 libxml.so -> libxml.so.1.8.14
lrwxrwxrwx 1 root root     16 Apr  4  2002 libxml.so.1 -> libxml.so.1.8.14
-rwxr-xr-x 1 root root 498438 Aug 13  2001 libxml.so.1.8.14

If I'm the author of libxml and I come out with a new version, libxml 2.0.0 that breaks interface compatiblity with the previous version, I can install it as libxml.so.2, and libxml.so.2.0.0. Note that it is up to the application programmer to be responsible about what he links to. If I'm really anal, I can link directly to libxml.so.1.8.14 and any other version will result in my program not running. Or I can link against libxml.so.1 and hope that the libxml developer doesn't break symbol compatibility on me in the 1.X version. Or if you don't care and are reckless, just link to libxml.so and get whatever version there is. Sometimes, when enough people do this, the library author has to get creative with later versions. Hence, libxml2:

lrwxrwxrwx 1 root root     17 Apr  4  2002 libxml2.so.2 -> libxml2.so.2.4.10
-rwxr-xr-x 1 root root 692727 Nov 13  2001 libxml2.so.2.4.10

Note that there's no libxml2.so in this one. Looks like the developer got fed up with irresponsible application developers.