I would like to understand the term system call. I am familiar that system calls are used to get kernel services from a userspace application.

The part i need clarification with is the difference between a system call and a c implementation of the system call.

Here is a qoute that confuses me:

On Unix-like systems, that API is usually part of an implementation of the C library (libc), such as glibc, that provides wrapper functions for the system calls, often named the same as the system calls that they call

What are the system calls that they call? Where is their source? Can I include them directly in my code?

Is the system call in a generic sense just a POSIX defined interface but to actually see the implementation one could examine the c source and in it see how the actual userspace to kernel communication actually goes?

Background note: I'm trying to understand if, in the end, each c function ends up interacting with devices from /dev.

I would like to understand the term "system call". I am familiar that system calls are used to get kernel services from a userspace application.

The part i need clarification with is the difference between a "system call" and a "C implementation of the system call".

Here is a quote that confuses me:

On Unix-like systems, that API is usually part of an implementation of the C library (libc), such as glibc, that provides wrapper functions for the system calls, often named the same as the system calls that they call

What are the "system calls that they call"? Where is their source? Can I include them directly in my code?

Is the "system call" in a generic sense just a POSIX defined interface but to actually see the implementation one could examine the C source and in it see how the actual userspace to kernel communication actually goes?

Background note: I'm trying to understand if, in the end, each c function ends up interacting with devices from /dev.