深度好文|面试官：进程和线程，我只问这19个问题

pthread_create               创建一个新线程pthread_exit                 结束调用的线程pthread_join                 等待一个特定的线程退出pthread_yield                释放CPU来运行另外一个线程pthread_attr_init            创建并初始化一个线程的属性结构pthread_attr_destroy         删除一个线程的属性结构

void F() {    cout << "a" << endl;}
int main() {    std::thread r(F);    r.detach();    std::this_thread::sleep_for(std::chrono::seconds(20));    return 0;}

#include #include #include int main() {    int _pipe[2];    int ret = pipe(_pipe);    if (ret < 0) {        perror("pipe\n");    }    pid_t id = fork();    if (id < 0) {        perror("fork\n");    } else if (id == 0) {  // 子进程        close(_pipe[1]);        int j = 0;        char _mesg[100];        while (j < 100) {            memset(_mesg, '\0', sizeof(_mesg));            read(_pipe[0], _mesg, sizeof(_mesg));            printf("%s\n", _mesg);            j++;        }    } else {  // 父进程        close(_pipe[0]);        int i = 0;        char *mesg = NULL;        while (i < 100) {            mesg = "父进程来写消息了";            write(_pipe[1], mesg, strlen(mesg) + 1);            sleep(1);            ++i;        }    }    return 0;
}

ls | less

std::string GetCmdResult(const std::string &cmd, int max_size = 10240) {    char *data = (char *)malloc(max_size);    if (data == NULL) {        return std::string("malloc fail");    }    memset(data, 0, max_size);    const int max_buffer = 256;    char buffer[max_buffer];    // 将标准错误重定向到标准输出    FILE *fdp = popen((cmd + " 2>&1").c_str(), "r");    int data_len = 0;
    if (fdp) {        while (!feof(fdp)) {            if (fgets(buffer, max_buffer, fdp)) {                int len = strlen(buffer);                if (data_len + len > max_size) {                    cout << "data size larger than " << max_size;                    break;                }                memcpy(data + data_len, buffer, len);                data_len += len;            }        }        pclose(fdp);    }    std::string ret(data, data_len);    free(data);    return ret;}

int mkfifo(const char* filename, mode_t mode);

// 创建和访问一个消息队列int msgget(key_t, key, int msgflg);// 用来把消息添加到消息队列中int msgsend(int msgid, const void *msg_ptr, size_t msg_sz, int msgflg);// msg_ptr是结构体数据的指针，结构第一个字段要有个类型：struct Msg {    long int message_type;    // 想要传输的数据};// 从消息队列中获取消息int msgrcv(int msgid, void *msg_ptr, size_t msg_st, long int msgtype, int msgflg);// 用来控制消息队列，不同的command参数有不同的控制方式int msgctl(int msgid, int command, struct msgid_ds *buf);

#include #include #include #include #include 
#include #include #include 
using namespace std;
#define BUFFER_SIZ 20
typedef struct {    long int msg_type;    char text[BUFFER_SIZ];} MsgWrapper;
void Receive() {    MsgWrapper data;    long int msgtype = 2;    int msgid = msgget((key_t)1024, 0666 | IPC_CREAT);    if (msgid == -1) {        cout << "msgget error \n";        return;    }    while (true) {        if (msgrcv(msgid, (void *)&data, BUFFER_SIZ, msgtype, 0) == -1) {            cout << "error " << errno << endl;        }        cout << "read data " << data.text << endl;        if (strlen(data.text) > 6) {  // 发送超过6个字符的数据，结束            break;        }    }    if (msgctl(msgid, IPC_RMID, 0) == -1) {        cout << "msgctl error \n";    }    cout << "Receive ok \n";}
void Send() {    MsgWrapper data;    long int msgtype = 2;    int msgid = msgget((key_t)1024, 0666 | IPC_CREAT);    if (msgid == -1) {        cout << "msgget error \n";        return;    }    data.msg_type = msgtype;    for (int i = 0; i < 10; ++i) {        memset(data.text, 0, BUFFER_SIZ);        char a = 'a' + i;        memset(data.text, a, 1);        if (msgsnd(msgid, (void *)&data, BUFFER_SIZ, 0) == -1) {            cout << "msgsnd error \n";            return;        }        std::this_thread::sleep_for(std::chrono::seconds(1));    }    memcpy(data.text, "1234567", 7);    if (msgsnd(msgid, (void *)&data, BUFFER_SIZ, 0) == -1) {        cout << "msgsnd error \n";        return;    }}
int main() {    std::thread r(Receive);    r.detach();    std::thread s(Send);    s.detach();    std::this_thread::sleep_for(std::chrono::seconds(20));    return 0;}
输出：root@iZuf64idor3ej648ciairaZ:~# ./a.outread data aread data bread data cread data dread data eread data fread data gread data hread data iread data jread data 1234567Receive ok