通过管道传递变量，通过分叉进程执行Shell命令

2 回答

• 1

  当您使用 dup 时，您使用管道输入模拟子进程 stdin ，因此当您执行 sort 而没有任何参数时，它会从 stdin 读取并读取直到它看到EOF，因此您必须写入管道然后关闭它 .

  #include <stdio.h>
  #include <string.h>
  #include <unistd.h>
  #include <stdlib.h>
  #include <sys/wait.h>
  
  int main(){
  
     int pipefd[2];
     //create a pipe before you fork a child process
     pipe(pipefd);
  
     pid_t cpid = fork();
     if(cpid < 0){
         perror("Fork");
     } else if(cpid == 0) {
         printf("This is child process\n");
  
         close(pipefd[1]);
         close(0);
  
         dup2(pipefd[0],0);
  
         execlp("sort", "sort", NULL);
  
         exit(0);
  
    } else {
        printf("This is parent process\n");
        close(pipefd[0]);
  
        char *sort_array[] = {"hello", "amigos", "gracias", "hola"};
        for (int i=0; i<4; i++){
            write(pipefd[1],sort_array[i],strlen(sort_array[i]));
            write(pipefd[1], "\n",1);
        }
        close(pipefd[1]);
  
  
        int cstatus;
        wait(&cstatus);
  
      }
  }
  

  回复于 2024-04-28T15:23:21+08:00
• 0

  pipe(pipefd);  // N.B. failed to check the return value, potential error
  
  //create a pipe before you fork a child process
  pid_t cpid = fork();
  if (cpid < 0)  // `if` is a language keyword, not a function, space after
  {              // opening brace on next line makes reading code easier
      perror("Fork");
  }
  else if (cpid == 0)
  {
      printf("This is child process\n");
  
      close(pipefd[1]);  // closing "write" end of pipe in child
      close(0);          // closing stdin in child
  
      dup2(pipefd[0],0); // returned handle is not stored, see https://linux.die.net/man/3/dup2
  
      execlp("cat", "cat", NULL);  // function prototype is int execlp(const char *file, const char *arg, ...);
                                   // what are you trying to accomplish?
  
      exit(0);
  }
  else
  {
      printf("This is parent process\n");
      close(pipefd[0]);  // close "read" end of pipe in parent process
  
      write(pipefd[1], "s.txt", 5);  // write text into pipe
  
      int cstatus;
      wait(&cstatus);    // wait for ??? something
  }
  

  您希望将其名称传递到管道的文件打开并写入输出的位置在哪里？

  回复于 2024-04-28T15:23:21+08:00