C叉兩個孩子和父母與子女之間的管道

Question

我想叉兩個孩子。父母讀取發送到管道的行。孩子讀它並將其寫入另一個管道，最後child2讀取它。但是，輸出始終是父項。謝謝！

#define MAX 80 

void child(); 
void parent(); 
void childtwo(); 
char * getli(); 
void printline(char *buffer, int count); 
char * convertCase(char *str); 

int pipe1[2]; 
int pipe2[2]; 
int main(int argc, char **argv) 
{ 
    pipe(pipe1); 
    pipe(pipe2); 
    if(fork()){ 
    if(fork()){ 
     printf("1st\n"); 
     parent(); 
      exit(0); 
    } 
    else{ 
     printf("3rd\n"); 
     childtwo(); 
     exit(0); 
    } 
    } 
    else{ 
    printf("2nd\n"); 
    child(); 
    exit(0); 
    } 
} 

void child(){ 
    char *buf; 
    int count = 0; 
    close(pipe1[1]); 
    close(pipe2[0]); 
    while(1){ 
    buf = (char *) malloc(sizeof(char)*MAX); 
    read(pipe1[0], buf, MAX); 
    if (strcmp(buf,"quit")== 0){ 
    printf("Child is leaving\n"); 
    free(buf); 
    break; 
    } 
    else{ 
    printf("Child: "); 
    printline(buf,strlen(buf)); 
    write(pipe2[1],buf, strlen(buf)+1); 
    free(buf); 
     } 
    close(pipe2[1]); 
    close(pipe1[0]); 
    exit(0); 
    } 
} 

void childtwo() 
{ 
    char *buf; 
    int count = 0; 
    close(pipe2[1]); 
    buf = (char *) malloc(sizeof(char)*MAX); 
    while(1){ 
    buf = (char *) malloc(sizeof(char)*MAX); 
    read(pipe2[0], buf, MAX); 
    if (strcmp(buf,"quit")== 0){ 
     printf("Childtwo is leaving\n"); 
     free(buf); 
     break; 
    } 
    else{ 
     printf("Childtwo:"); 
     printline(buf,strlen(buf)); 
     free(buf); 
    } 
    } 
    close(pipe2[0]); 
    exit(0); 
} 

void parent(){ 
    char * buffer; 
    int count = 0, done=0; 
    close(pipe1[0]); 
    while (done != 1){ 
    printf("parent getting line: "); 
    buffer = getli(); 
    write(pipe1[1],buffer, strlen(buffer)+1); 
    if (strcmp(buffer,"quit")== 0){ 
     puts("parent goes away"); 
     free(buffer); 
     break; 
    } 
    free(buffer); 
    } 
    close(pipe1[1]); 
    exit(0); 
} 

Answer 1

我的猜測是，它適用於第一行，但不適用於任何其他。

這是因爲第一個子進程（在child函數中）在讀取其輸入後退出。您可能打算將close和exit調用放在循環之外。