Notes and Reflections on Books and Media
by Hannah Leitheiser
linux kernel development, 3rd edition
the next chapter is on linux system calls (programs requesting the kernel do things). there are about 300 calls in the linux kernel (https://filippo.io/linux-syscall-table/). syscalls have to be fast, yet secure, obviously, as they are used frequently and run in kernel space. the book discussed how to implement your own syscalls, and i tried for awhile to at least implement the write() call in c without header files. sadly the book's method is depreciated and i gave up. anyway, here's a syscall for write (happens to be numbered 1 on my system).