#include <assert.h>
#include <sys/ptrace.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <syscall.h>
#include <sys/reg.h>
#include <stdio.h>

#ifdef __x86_64__
#define SYSCALL_OFF (ORIG_RAX * 8)
#else
#define SYSCALL_OFF (ORIG_EAX * 4)
#endif

int main()
{
  pid_t const child = fork();

  if (child == -1) perror("fork failed");

  if(child == 0)
  {
    ptrace(PTRACE_TRACEME, 0, NULL, NULL);
    execl("/usr/bin/whoami", "whoami", NULL);
    perror("execl failed");
  }
  
  for(;;)
  {
    int status;
    wait(&status);

    if(WIFEXITED(status)) break;

    assert(WIFSTOPPED(status) && WSTOPSIG(status) == SIGTRAP);

    long const syscall = ptrace(PTRACE_PEEKUSER, child, SYSCALL_OFF, NULL);
    printf("%ld ", syscall);

    ptrace(PTRACE_SYSCALL, child, NULL, NULL);
  }

  printf("\n");

  return 0;
}