Syntax of common calls:

       int select(int n, fd_set  *readfds,  fd_set  *writefds,  
            fd_set  *exceptfds, struct timeval *timeout);
       FD_CLR(int fd, fd_set *set);
       FD_ISSET(int fd, fd_set *set);
       FD_SET(int fd, fd_set *set);
       FD_ZERO(fd_set *set);

       int pipe(int filedes[2]);
       int execlp(const char *file, const char *arg, ...);
       int dup(int oldfd);
       int dup2(int oldfd, int newfd);
       pid_t fork(void);
       pid_t wait(int *status);

       int setjmp(jmp_buf env);
       int sigsetjmp(sigjmp_buf env, int savesigs);

       typedef void (*sighandler_t)(int);
       sighandler_t signal(int signum, sighandler_t handler);
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       unsigned int alarm(unsigned int seconds);   /* Relevant signal: SIGALRM */