第五章 进程API

1.

#include <sys/types.h>
#include <unistd.h>
#include <iostream>
using namespace std;
int main()
{
    int x = 100;
    cout << x << endl;
    int pid = fork();
    if (pid == 0) // child
    {
        cout << "child:" << x << endl;
        x = 1;
        cout << "child:" << x << endl;
    }
    else // father
    {
        cout << "father:" << x << endl;
        x = 200;
        cout << "father:" << x << endl;
    }
    return 0;
}

2.

#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <iostream>
#include <fcntl.h>
#include <cstring>
using namespace std;
int main()
{
    int fd = open("tmp.txt", O_RDWR);
    int pid = fork();
    char read_buf[20], write_buf[20] = "rising!\0";
    if (pid == 0) // child
    {
        int len = read(fd, read_buf, strlen(write_buf));
        cout << "son read len:" << len << endl;
        for (int i = 0; i < len; i++)
            cout << "son:" << read_buf[i] << endl;

        len = write(fd, write_buf, strlen(write_buf));
        if (len > 0)
            cout << "son write success" << endl;
    }
    else // father
    {
        int len = read(fd, read_buf, strlen(write_buf));
        cout << "father read len:" << len << endl;
        for (int i = 0; i < len; i++)
            cout << "father:" << read_buf[i] << endl;

        len = write(fd, write_buf, strlen(write_buf));
        if (len > 0)
            cout << "father write success" << endl;
    }
    return 0;
}

5.

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <unistd.h>
#include <iostream>
#include <fcntl.h>
#include <cstring>
using namespace std;
int main()
{
    int pid = fork();

    if (pid == 0) // child
    {
        int t = 0;
        int res = wait(&t);
        cout << "son res:" << res << endl
             << "son t:" << t << endl;
    }
    else // father
    {
        int t = 0;
        int res = wait(&t);

        // int res = waitpid(pid, &t, 0);
        cout << "father res:" << res << endl
             << "father t:" << t << endl;
    }
    return 0;
}

7.

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <unistd.h>
#include <iostream>
#include <fcntl.h>
#include <cstring>
using namespace std;
int main()
{
    int pid = fork();

    if (pid == 0) // child
    {
        close(STDOUT_FILENO);
        printf("aaa\n");
    }
    else // father
    {
        int t;
        wait(&t);
    }
    return 0;
}

8.

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <unistd.h>
#include <iostream>
#include <fcntl.h>
#include <cstring>
using namespace std;
int main()
{
    int fd[2];
    pipe(fd);
    // string str;
    char str[10] = "hello";
    int pid1 = fork();
    if (pid1 == 0) // child
    {
        dup2(fd[1], STDOUT_FILENO);
        printf("%s\n", str); // 记得刷新缓冲区啊靠
    }
    else // father
    {
        int pid2 = fork();
        if (pid2 == 0) // child
        {
            dup2(fd[0], STDIN_FILENO);
            scanf("%s", str);
            printf("receive:%s\n", str);
        }
        else // father
        {
            int t;
            wait(&t);
            wait(&t);
        }
    }
    return 0;
}