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POUnnamed Pipes in UNIX child message doesn't get received by father while sending a string in C
 

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  1. POUnnamed Pipes in UNIX child message doesn't get received by father while sending a string in C
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    <p>I have two processes that I have created with two unnamed pipes, but I can't figure out why I can't send messages from the sons to the father. It appears that the father doesn't receive the string. The son is sending the right string; it just doesn't reach destination, can't figure out why ... Can you explain to me?</p> <pre><code>#include &lt;unistd.h&gt; #include &lt;sys/wait.h&gt; #include &lt;sys/types.h&gt; #include &lt;stdio.h&gt; #include &lt;strings.h&gt; #include &lt;sys/stat.h&gt; #include &lt;fcntl.h&gt; #include &lt;errno.h&gt; #include &lt;time.h&gt; #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 = &amp;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&lt;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&lt;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 &lt;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(&amp;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&lt;n_childs){ FD_SET(channel[0][0], &amp;read_set); for(i=0;i&lt;n_childs;i++){ FD_SET(channel[i][0], &amp;read_set); if(fd&lt;channel[i][0]){ fd=channel[i][0]; } } if(select(fd+1,&amp;read_set,NULL,NULL,NULL)&gt;0){ for(i=0;i&lt;n_childs;i++){ if(FD_ISSET(channel[i][0], &amp;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&lt;n_childs;i++){ wait(&amp;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&lt;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&gt;0 &amp;&amp; init_read&lt;=n_lines){ for(i = 0;i&lt;init_read;i++){ fgets(str, sizeof str, fp); for(i = init_read;i&lt;n_lines;i++){ fgets(str, sizeof str, fp); strcpy(*pointer, str); //copia para a posicao actula do ponteiro pointer++; } } } if(init_read&lt;=n_lines &amp;&amp; init_read==0){ for(i = init_read;i&lt;n_lines;i++){ fgets(str, sizeof str, fp); strcpy(*pointer, str); //copia para a posicao actula do ponteiro pointer++; } } fclose(fp); } </code></pre>
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    1. USJonathan Leffler
    1. USexceltior
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      1. POUnnamed Pipes in UNIX child message doesn't get received by father while sending a string in C
      1. USexceltior
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    1. COYou've got a buffer overflow bug at: `char get_file[strlen(filename)]; strcpy(get_file,filename);`. You need to use `strlen(filename)+1`...if you need to copy the file name for a second time, which is unlikely. In fact, it isn't clear why you need to copy the file name at all.
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      1. POUnnamed Pipes in UNIX child message doesn't get received by father while sending a string in C
      1. USJonathan Leffler
    2. COThanks for the answer,i forgot i had two variables repeated,but i was testing the child to see if it read the files and it did read everything from the file, so there must be other problem ...
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      1. POUnnamed Pipes in UNIX child message doesn't get received by father while sending a string in C
      1. USexceltior
 

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