Linux多线程 作业

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要求

父进程创建 3 个进程，父进程等待子进程 2 运行完成之后，自行退出；其中子进程 1 运行系统命令“cp /bin/ls /tmp”；等待 2 秒后退出；子进程 2 使用标准 I/O 函数打开文件 src_file，向其内写入“this is process 2\n”，之后等待 5 秒后退出；子进程 3 处理为守护进程，每隔 5 秒向日志文件/var/log/messages 写入“this is process 3\n”

提交形式

  1. 代码
  2. 运行结果截图

Code

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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <syslog.h>
#include <sys/types.h>
#include <sys/wait.h>

int main() {
  pid_t child, child1, child2, daemon;
  int i, fd, sid;
  char* message1 = "this is a process 2.\n";
  char* message2 = "this is a process 3.\n";

  child1 = fork();

  if (child1 < 0) {
    printf("Child1 fork error.\n");
    exit(1);
  } else if (child1 == 0) { // child1 thread
    if (execlp("cp", "cp", "/bin/ls", "/tmp", NULL) < 0) {
      printf("Child1");
    }
    sleep(2);
    exit(0);
  } else { // father thread

    child2 = fork();

    if (child2 == -1) {
      printf("Child2 fork error.\n");
      exit(1);
    } else if (child2 == 0) { // child2 thread
      if ((fd = open("./src_file", O_CREAT|O_WRONLY|O_APPEND, 0600)) < 0) {
        printf("Open file error.\n");
        exit(1);
      }
      write(fd, message1, strlen(message1) + 1);
      sleep(5);
      exit(0);
    }

    do {
      child = waitpid(child1, NULL, WNOHANG);
      if (child == 0) {
        printf("child1 is running.\n");
        sleep(1);
      }
    } while (child == 0);

    do {
      child = waitpid(child2, NULL, WNOHANG);
      if (child == 0) {
      printf("child2 is running.\n");
         sleep(1);
      }
    } while (child == 0);

    daemon = fork(); // fork daemon

    openlog("test_syslog", LOG_PID, LOG_DAEMON); // open syslog

    if (daemon < 0) {
      printf("Daemon fork error.\n");
      exit(1);
    } else if (daemon > 0) {
      exit(0); // father thread exit
    }

    if ((sid = setsid()) < 0) {
      syslog(LOG_ERR, "%s\n", "setsid");
      exit(1);
    }

    if ((sid = chdir("/")) < 0) {
      syslog(LOG_ERR, "%s\n", "chdir");
      exit(1);
    }

    // start make daemon thread
    umask(0);
    for (i = 0; i < getdtablesize(); i++) {
      close(i);
    }

    while (1) { // start run daemon thread
      if ((fd = open("/var/log/message", O_CREAT|O_WRONLY|O_APPEND, 0600)) < 0) { // get the fildes
        syslog(LOG_ERR, "open");
        exit(1);
      }

      write(fd, message2, strlen(message2) + 1);
      close(fd);
      sleep(5);
    }

    closelog();
    exit(0);
  }

  exit(0);
}