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我有两个使用两个未命名管道创建的进程，但我无法弄清楚为什么我不能将消息从儿子发送给父亲。父亲似乎没有收到字符串。儿子正在发送正确的字符串；它只是没有到达目的地，无法弄清楚为什么......你能给我解释一下吗？

#include <unistd.h>
#include <sys/wait.h>
#include <sys/types.h>
#include <stdio.h>
#include <strings.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <time.h>

    #define max_chars_string 1000
    #define n_childs 2

    pid_t childs[n_childs];
    int channel[n_childs][2];

    void read_lines(char * filename, char (*pointer)[max_chars_string],int init_read,int n_lines);
    void get_strings_hash(char (*pointer_strings)[max_chars_string],char (*pointer_hashes)[max_chars_string],int total_lines);

    void worker(int mypipe,char filename[],int n_lines){ // meter as funcoes de ler passwords no filho
        int resources[2];// numero de linhas que cada processo tem de ler
        int i = 0;

        //definicao arrays
        char strings_hashes[n_lines][max_chars_string];//aray de string com as strings lidas do ficheiro
            char * pointer_strings = &strings_hashes[0][0];//ponteiro para o inicio do array das hashes

        read_lines(filename,strings_hashes,0,n_lines); // le as strings do ficheiro e passa para o array

        for(i = 0;i<n_lines;i++){
            printf("%s \n",strings_hashes[i]);
        }
        printf("[%d] My parent is: %d\n", getpid(), getppid());

        //open pipe to write and close pipe to read

        close(channel[mypipe][0]);
        i = 0;
        int incr = 0;
        while (i<n_lines) {
            printf("[Son] Password sent e  %s: \n",strings_hashes[incr]);
             write(channel[mypipe][1], strings_hashes[incr], strlen(strings_hashes[incr]));
             incr++;
             i++;
        }
        exit(0);
    }

    int main(int argc, char **argv)
    {
        char *filename;
        int status;//status do processos filho
        int resources[2];// numero de linhas que cada processo tem de ler
        int n_lines; //numero de linhas do ficheiro
        int i = 0;

          // Create a pipe
        filename = (char*)malloc(strlen(argv[1])*sizeof(char)+1);

        if(argc !=3){
            fprintf(stderr, "Usage : %s [text_file] [cores]",argv[0]);
            exit(0);
        }

        strcpy(filename,argv[1]);

        char get_file [strlen(filename)];
        strcpy(get_file,filename);

     // start the processes
       for(i = 0; i <atoi(argv[2]);i++){
            pipe(channel[i]);
            childs[i] = fork();

            if(childs[i] == -1){
               perror("Failed to fork");
               return 1;
           }
           if (childs[i] == 0)
           {
              worker(i,get_file,n_lines);
           }
           close(channel[i][1]);
       }

               i = 0;
               int k = 0;
               int fd;
               fd_set read_set;
               FD_ZERO(&read_set);
               char string_lida [30];

               // working father
               printf("[%d] I'm the father!\n", getpid());
               printf("[Father]orking ...\n");

                //unammed_pipes connection
                while(k<n_childs){

                    FD_SET(channel[0][0], &read_set);
                    for(i=0;i<n_childs;i++){
                            FD_SET(channel[i][0], &read_set);
                            if(fd<channel[i][0]){      fd=channel[i][0];
                            }
                        }

                    if(select(fd+1,&read_set,NULL,NULL,NULL)>0){
                        for(i=0;i<n_childs;i++){
                            if(FD_ISSET(channel[i][0], &read_set)){                    
                                read(channel[i][0],string_lida,strlen(string_lida));
                                printf("[Father]pipe %d - string lida:%s\n",i,string_lida);

                                k++;                 
                            }
                        }
                    }
                    fd=1;
                }
              //
              //waiting for childs ...
            for(i=0;i<n_childs;i++){
                wait(&status);
                printf("waiting for childs \n");
              }

      return 0;
    }  


    void get_strings_hash(char (*pointer_strings)[max_chars_string],char (*pointer_hashes)[max_chars_string],int total_lines)//vai ao array de strings e corta a parte de hash e mete num array
    {
        int i = 0;
        char *strings;
        char *hash;

        for(i = 0;i<total_lines;i++){
                strings = (char*)malloc(strlen(pointer_strings)*sizeof(char)+1);
                strcpy(strings,*pointer_strings);
                hash = (char*)malloc(strlen(pointer_strings)*sizeof(char)+1);
                find_hash(strings,hash);
                strcpy(*pointer_hashes,hash);
            pointer_hashes++;
            pointer_strings++;
        }

    }


    void read_lines(char * filename, char (*pointer)[max_chars_string],int init_read,int n_lines){ 
        FILE *fp;
        char str[max_chars_string];
        int i =0;

        if((fp = fopen(filename, "r"))==NULL) {
          printf("Cannot open file.\n");
          exit(1);
        }

        if(init_read>0 && init_read<=n_lines){
         for(i = 0;i<init_read;i++){
             fgets(str, sizeof str, fp);
           for(i = init_read;i<n_lines;i++){
               fgets(str, sizeof str, fp);
               strcpy(*pointer, str); //copia para a posicao actula do ponteiro
               pointer++;
           }
         }
        }
        if(init_read<=n_lines && init_read==0){
           for(i = init_read;i<n_lines;i++){
                fgets(str, sizeof str, fp);
               strcpy(*pointer, str); //copia para a posicao actula do ponteiro
               pointer++;
           }
         }


      fclose(fp);
    }
4

1 回答 1

1

一个问题是这一行：

read(channel[i][0],string_lida,strlen(string_lida));

因为你没有初始化string_lida，所以strlen可能会返回任何东西，但我猜它会返回 0（字符串为空），所以你从来没有读过任何东西。你想要sizeof(string_lida)。然后，您需要手动 NUL 终止字符串，string_lida因为读取不会这样做。因此，您需要检查 的返回值read以查看读取了多少个字符（或者它是否是 EOF）。

您也只等待读取总共 n_childs 个字符串——如果每个孩子发送多个字符串，您将不会得到其中的大部分。

于 2012-10-12T23:29:35.177 回答