gistfile1.c

#include "tlpi_hdr.h"

int
main(int argc, char *argv[])
{
    printf("Hello world\n");
    write(STDOUT_FILENO, "Ciao\n", 5);
    if (fork() == -1)
        errExit("fork");
    /* Both child and parent continue execution here */
    exit(EXIT_SUCCESS);
}

./a.out
输出:
Hello world
Ciao

./a.out > /tmp/a
输出
Ciao
Hello world
Hello world