空调系统调用管道，叉和EXECL [英] C system calls pipe, fork, and execl

问题描述

我fork（）的倒是一个子进程，并在它们之间建立管道和我能够参数ARGV发[1]给孩子。我希望孩子采取从argv的提供该文件名[1]，并执行execl的（/斌/猫，猫，（字符*）0）;
我怎么路线输送到孩子到execl的文件名？

附上我的code为clearity：

  INT主（INT ARGC，字符** argv的）{
   INT FDS [2];
   炭缓冲器[100];
   INT状态;   如果（管（FDS）== -1）{
      PERROR（管子创建失败）;
      出口（EXIT_FAILURE）;
   }   开关（叉（））​​{    案件0：//子
       关闭（FDS [1]）; //关闭标准输出所以只能做标准输入
       读（FDS [0]，缓冲液，strlen的（的argv [1]））;
       的printf（从父项：％S \\ N的argv [1]）;
       EXECL（/斌/猫，猫，（字符*）0）;
       PERROR（猫失败）;
       出口（20）;
       打破;      案例-1：// fork失败
       PERROR（fork失败）;
       出口（EXIT_FAILURE）;      默认：//父
       关闭（FDS [0]）; //关闭标准输入所以唯一能做的标准输出
       写（FDS [1]，ARGV [1]的strlen（ARGV [1]））;
   }   回报（EXIT_SUCCESS）;
}
 

解决方案

为什么要通过管道写文件名时叉（） preserves 的argv [1] ？

你不检查你的读长对你的缓冲区长度。

您不是发射尾随NUL（的strlen（）不包括），这样的文件名字符串在终止缓存未初始化。追加 +1 所有的的strlen（）值来纠正。然后，

  EXECL（/斌/猫，猫，缓冲，（字符*）0）;
 

会做你问什么，但你已经关闭标准输出所以猫（不是 EXECL ）会失败，而你没有检查它的退出code。

I fork()'d a child process and created pipes between them and am able to send argument argv[1] to the child. I want the child to take that filename provided from argv[1] and perform an execl("/bin/cat","cat",(char *) 0); How do I route the filename piped to the child to the execl?

Enclose is my code for clearity :

int main(int argc, char ** argv){
   int fds[2];
   char buffer[100];
   int status;

   if(pipe(fds) == -1){
      perror("pipe creation failed");
      exit(EXIT_FAILURE);
   }

   switch (fork()){

    case 0://child
       close(fds[1]); //close stdout so can only do stdin
       read(fds[0],buffer,strlen(argv[1]));
       printf("from parent: %s\n",argv[1]);
       execl("/bin/cat","cat",(char*)0);
       perror("cat failed");
       exit(20);
       break;

      case -1: //fork failure
       perror("fork failure");
       exit(EXIT_FAILURE);

      default: //parent 
       close(fds[0]); //close stdin so only can do stdout
       write(fds[1],argv[1], strlen(argv[1]));             
   }   

   return (EXIT_SUCCESS);
}

解决方案

Why are you writing the filename through the pipe when fork() preserves argv[1]?

You're not checking your read length against your buffer length.

You're not transmitting the trailing nul (strlen() doesn't include it) so the filename string's terminator in buffer is uninitialized. Append +1 to all of your strlen() values to correct that. Then,

execl("/bin/cat","cat",buffer,(char*)0);

will do what you ask for, but you've closed stdout so the cat (not the execl) will fail, and you're not checking its exit code.

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