使用管道

Question

我正在尝试完成这项工作，但没有运气，基本上我需要写入管道，然后使管道返回我发送的文本。我有一个 server.c 和 client.c ，所以我让 server.c 运行...，打开一个新终端，然后运行客户端..问题是客户端在我运行它时不执行任何操作..我我确信我错过了一些东西..比如关闭管道。我不确定..我真的很感激一些指导

server.c

#include <stdio.h>
#include <errno.h>
#include <ctype.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#define PIPE1      "PIPE1"
#define PIPE5      "PIPE5"

#define MAX_BUF_SIZE    255

int main(int argc, char *argv[])
{
    int rdfd1,rdfd2,rdfd3,rdfd4, wrfd1,wrfd2,wrfd3,wrfd4,ret_val, count, numread1,numread2,numread3,numread4;
    char buf1[MAX_BUF_SIZE];
    char buf2[MAX_BUF_SIZE];
    char buf3[MAX_BUF_SIZE];
    char buf4[MAX_BUF_SIZE];

    /* Create the first named - pipe */
    ret_val = mkfifo(PIPE1, 0666);


    if ((ret_val == -1) && (errno != EEXIST)) {
        perror("Error creating the named pipe");
          return 1; 
    }



    ret_val = mkfifo(PIPE5, 0666);

    if ((ret_val == -1) && (errno != EEXIST)) {
        perror("Error creating the named pipe");
        return 1; 
    }

    /* Open the first named pipe for reading */
    rdfd1 = open(PIPE1, O_RDONLY);


    /* Open the first named pipe for writing */
    wrfd1 = open(PIPE5, O_WRONLY);


    /* Read from the pipes */
    numread1 = read(rdfd1, buf1, MAX_BUF_SIZE);


    buf1[numread1] = '0';

    printf("Server : Read From the  pipe : %sn", buf1);


    /* 
     * Write the converted content to 
     * pipe 
     */    
   write(wrfd1, buf1, strlen(buf1));

}

client.c

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <ctype.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#define PIPE1      "PIPE1"
#define PIPE5      "PIPE5"


#define MAX_BUF_SIZE    255


int main(int argc,  char *argv[ ]) {
   pid_t childpid;             
   int error;                  
   int i;                     
   int nprocs;                
           /* check command line for a valid number of processes to generate */

   int wrfd1, rdfd1, numread;
    char rdbuf[MAX_BUF_SIZE];

   if ( (argc != 2) || ((nprocs = atoi (argv[1])) <= 0) ) {
       fprintf (stderr, "Usage: %s nprocs\n", argv[0]);
       return 1; 
   }  



   for (i = 1; i < nprocs;  i++) {  
       /* create the remaining processes */

            if ((childpid = fork()) == -1) {
                  fprintf(stderr, "[%ld]:failed to create child %d: %s\n", (long)getpid(), i, strerror(errno));
                   return 1; 
                } 

          /* Open the first named pipe for writing */
          wrfd1 = open(PIPE5, O_WRONLY);

          /* Open the second named pipe for reading */
         rdfd1 = open(PIPE1, O_RDONLY);


         if (childpid)
         break;

           char string1[100];

            if(sprintf(string1, "This is process %d with ID %ld and parent id %ld\n", i,  (long)getpid(), (long)getppid())) {
              write(wrfd1,string1, strlen(string1));
              }

         /* Read from the pipe */
         numread = read(rdfd1, rdbuf, MAX_BUF_SIZE);

         rdbuf[numread] = '0';

         printf("Full Duplex Client : Read From the Pipe : %sn", rdbuf);    
      } 


   return 0; 
}  

Answer 1

看起来服务器和客户端都从 PIPE1 读取并写入 PIPE5。难道其中一个不应该写入 PIPE1 以便另一个可以从另一端读取它吗？

另外，如果您使用 ./client 1 进行测试，您的 for (i = 1; i < nprocs; i++) 循环将永远不会执行。

最后一件事，请参阅这个问题。我不完全确定它是否适用于您的代码，但值得记住。

Answer 2

这行不应该是 '\0' 吗？

buf1[numread1] = '0';