I just want to ask, can I pass a pointer to a structure using pipes in
C. I really want to pass the pointer to a head of a linked list, but I
get nothing. The code is:
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
typedef struct {
int whoami;
int data;
struct datagram *next;
struct datagram *prev;
} datagram;
void parent_to_child(int input[2], int output[2]) {
datagram *head, *trav, *temp;
int i=1, num_input;
close(input[1]);
close(output[0]);
/* Receive input from console and create the node associated */
do {
printf("\nInput number %d : ",i);
scanf("%d",&num_input);
temp = (datagram*)malloc(sizeof(datagram));
temp->whoami = i;
temp->data = num_input;
temp->next = temp->prev = NULL;
i++;
/* Passes to child created node */
write(output[1],(void*)&temp,sizeof(datagram*));
} while(num_input>0);
/* Receives head node of the list */
read(input[0],(void*)&head,sizeof(datagram*));
/* Traverses and prints the elements of the list */
for(trav=head,i=1;trav!=NULL;trav=trav->next,i++) {
printf("\nNumber %d is %d, which has been inputed
%dth.",i,trav->data,trav->whoami);
}
close(input[0]);
close(output[1]);
exit(0);
}
void child_to_parent(int input[2], int output[2]) {
datagram *head, *tail, *temp, *trav, *mark;
int i;
close(input[1]);
close(output[0]);
/* Sentinel node */
head = (datagram*)malloc(sizeof(datagram));
head->whoami = -1;
head->data = -1;
head->next = NULL;
tail = head;
/* Receives node and adds to list until encountered data zero */
while(1) {
read(input[0],(void*)&temp,sizeof(datagram*));
printf("temp->whoami = %d, temp->data =
%d",temp->whoami,temp->data);
tail->next = temp;
temp->prev = tail;
tail = tail->next;
}
write(output[1],(void*)&head,sizeof(datagram*));
close(input[0]);
close(output[1]);
exit(0);
}
int main() {
pid_t child_pid;
int child_status, pipe1[2], pipe2[2], piperet = 0;
piperet += pipe(pipe1);
piperet += pipe(pipe2);
if(piperet<0) {
perror("pipe");
exit(1);
}
child_pid = fork();
switch(child_pid) {
case -1 : {
perror("fork");
exit(1);
}
case 0 : {
child_to_parent(pipe2,pipe1);
}
default : {
parent_to_child(pipe1,pipe2);
}
}
}
Can anyone tell me what is wrong? I would appreciate any response.
--
James Matthew B. Miraflor
2002-17119
BS Computer Science
University of the Philippines
Manila
(+63)02-2876007
+639197101941
Block 49 Lot 29 Phase 3 E2
Dagat-dagatan, Malabon City
Philippines
___________________________________________________________
"(One) wins his battles by making no mistakes. Making no mistakes
is what establishes the certainty of victory, for it means conquering
an enemy that has already been defeated."
Sun Tzu
The Art of War
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