The other day, colleague showed me a (pretty basic) terminal emulator written in one-shot by Opus. Kicker is - that was compiled to a 30 KB static binary. That's right. No libX11, no libXfont, not even libc.
My terminal emulator using the same binding also started out hand-written but Claude overhauled that too recently and it knows vtxx escape codes far better than me too.
static inline long read(int fd, void *buf, long count) {
register long rax asm("rax") = __NR_read;
register long rdi asm("rdi") = (long)fd;
register long rsi asm("rsi") = (long)buf;
register long rdx asm("rdx") = count;
asm volatile(
"syscall"
: "+r"(rax)
: "r"(rdi), "r"(rsi), "r"(rdx)
: "rcx", "r11", "memory"
);
return rax;
}In my memory the syscall ABI has changed a few times (i386 had int $0x80, then sysenter, then abstracting it in the vdso, then amd64 has 'syscall'), so it may be easier to let the kernel header provide the mechanism.