I'm currently trying to port a C application to AIX and am getting confused. What are .a and .so files and how are they used when building/running an application?
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c
unix
compilation
shared-libraries
.a
.a files are usually libraries which get statically linked (or more accurately archives), and
.so are dynamically linked libraries.
To do a port you will need the source code that was compiled to make them, or equivalent files on your AIX machine.
They are used in the linking stage. .a files are statically linked, and .so files are sort-of linked, so that the library is needed whenever you run the exe.
You can find where they are stored by looking at any of the lib directories... /usr/lib and /lib have most of them, and there is also the LIBRARY_PATH environment variable.
Wikipedia is a decent source for this info.
To learn about static library files like .a read Static libarary
To learn about shared library files like .so read Library_(computing)#Shared_libraries On this page, there is also useful info in the File naming section.
.a are static libraries. If you use code stored inside them, it's taken from them and embedded into your own binary. In Visual Studio, these would be .lib files.
.so are dynamic libraries. If you use code stored inside them, it's not taken and embedded into your own binary. Instead it's just referenced, so the binary will depend on them and the code from the so file is added/loaded at runtime. In Visual Studio/Windows these would be .dll files (with small .lib files containing linking information).
Source: Stackoverflow.com