An SO file, also known as a shared object file, is a type of file used by Linux-based operating systems to store executable code and share it between different programs. It contains compiled machine code that can be loaded into the memory of a running process, allowing it to access and use the functions provided by the shared library.

Shared libraries are collections of pre-written functions and procedures that can be used by multiple programs. By using a shared library, programmers can reduce the size of executable files and speed up program compilation time, since they do not need to write and compile every function from scratch.

In a typical system, there are many shared libraries installed, each providing a set of functions that can be used by multiple programs. When a program needs to use a function from a shared library, it first makes a reference to a symbol (function name) defined in the library. The operating system then searches for the symbol in the library and loads the necessary object file into memory.

SO files can be created by compiling source code using a specific set of flags that generate position-independent machine code. This code can be loaded into any memory address, allowing the shared library to be loaded at different locations in memory for each process that uses it.

In addition, SO files can be dynamically linked to other shared libraries or objects, allowing them to interact with each other and share resources. This can be done at runtime, allowing a program to load and unload libraries as needed, and to use different versions of the same library for different processes.

One common use of SO files is in the field of system administration, where they are often used to update or replace shared libraries without disrupting running programs. For example, a security patch might require updating a specific shared library, but doing so could cause programs that depend on that library to fail. By using SO files, the updated library can be loaded into memory without affecting running programs, and the changes can take effect only when new programs are started.

In conclusion, an SO file is a file format used by Linux-based operating systems to store compiled machine code for shared libraries. It allows multiple programs to access and use the same set of pre-written functions and procedures, reducing the size of executable files and speeding up program compilation time. SO files can be dynamically linked and loaded into memory at runtime, allowing programs to interact with each other and share resources.