C struct values garbled - c

Question

Having the problem with the sender and receiver of the checksum. where I am using the struct to define the variables to be written into the pipe.
struct ANSWER
{
int arr[BUFFER];
int counter;
int ans;
}a;
The mechanism used for checksum is :
int chck(int value[],int count)
{
int i,sum=0,checksum;
for ( i=0; i<count; i++)
{
sum+=value[i];
}
printf("SUM IS :%d \n",sum);
checksum=checksum^sum;
printf("CHECKSUM IS : %d",checksum);
return checksum;
}
The main problem is in writing in the pipe as
write(pipe,a,sizeof(a));
This writes all the contains using struct.
While at receiver side having problem in retrieving the specific values
when I retrieve the values at receiver side I get garbled values in count and ans variables.
read(pipe,a,sizeof(a));
printf("COUNT : \n ",a.counter);
the values turn out to be garbled.
Main area:
void main(int argc, char * argv[])
{
int pipe,i;
pipe = open("devil",O_WRONLY);
if ( pipe == -1 )
{
printf("ERROR NO PIPE FOUND \n");
}
printf("ENTER NUMBER OF ELEMENT : ");
scanf("%d",a.counter);
for ( i=0; i<a.counter; i++)
{
printf("ENTER NUMBER :");
scanf("%d",&a.arr[i]);
}
a.ans=chck(a.arr,a.counter);
printf("CHECKSUM IS : %d \n",a.ans);
write(pipe,&a,sizeof(a));
}

Answer 1

Turning comment to answer, I suggest you add error checking to all your system and standard library calls (except printing to stdout/stderr, that's more clutter than it's worth for almost any app), something like:
int main(int argc, char * argv[])
{
int pipe, i;
pipe = open("devil",O_WRONLY);
if ( pipe == -1 )
{
perror("open pipe");
return EXIT_FAILURE;
}
printf("ENTER NUMBER OF ELEMENT : ");
if (scanf("%d",&a.counter) != 1)
{
fprintf(stderr, "scanf count IO or parse error, or EOF\n");
return EXIT_FAILURE;
}
for ( i=0; i<a.counter; i++)
{
printf("ENTER NUMBER :");
if (scanf("%d",&a.arr[i]) != 1)
{
fprintf(stderr, "scanf number IO or parse error, or EOF\n");
return EXIT_FAILURE;
}
}
a.ans=chck(a.arr,a.counter);
printf("CHECKSUM IS : %d \n",a.ans);
i = write(pipe,&a,sizeof(a));
if (i == -1)
{
perror("write to pipe");
return EXIT_FAILURE;
}
else if (i != sizeof(a))
{
fprintf(stderr, "write to pipe, partial write!\n");
return EXIT_FAILURE;
}
return EXIT_SUCCESS;
}
Notes: For pedantic code, write actually returns type ssize_t. I changed return type of main to int as that is required by standard. Please read manual page / docs of perror to understand what it does and how it prints the actual error message. EXIT_FAILURE and EXIT_SUCCESS are constants for the two standard-defined return values or exit codes, usually 1 and 0 respectively. And in a larger program, you would probably write helper functions or macros for error handling, and split the entire main function into multiple functions, to make the code look less cluttered.
Additionally, you use checksum variable uninitialized in chck function. You should probably initialize it to 0, something like:
int chck(int value[],int count)
{
int i = 0, sum = 0, checksum = 0;
....
In general, you should avoid having uninitialzied variables, it's too easy to forget when first using them, like demonstrated here... Also, turn on compiler warnings, so you will usually get a warning if you still do that accidentally.
One more bug: your first scanf was missing & to get pointer to a.counter (required for scanf, to actually modify the original variable). A good compiler may also be smart enough to warn about passing suspicious arguments to scanf.