How can i print every string in C pipes - arrays

Question

How can i print every string in C pipes i am stuck.
output like this
Received string: spike
Received string: spike
Received string: spike
but i want like this
Received string: spike
Received string: tom
Received string: jerry
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
int main(void)
{
int fd[2], nbytes;
pid_t childpid;
char string[3][10] = {
"spike",
"tom",
"jerry"};
char readbuffer[80];
pipe(fd);
if ((childpid = fork()) == -1)
{
perror("fork");
exit(1);
}
if (childpid == 0)
{
/* Child process closes up input side of pipe */
close(fd[0]);
/* Send "string" through the output side of pipe */
write(fd[1], string, (strlen(string) + 1));
exit(0);
}
else
{
/* Parent process closes up output side of pipe */
close(fd[1]);
/* Read in a string from the pipe */
nbytes = read(fd[0], readbuffer, sizeof(readbuffer));
for (int i = 0; i < 3; i++)
{
printf("Received string: %s \n", readbuffer);
}
}
return (0);
}

Answer 1

You've made several mistakes.
First of all, the child doesn't write the correct thing into the pipe.
Then you read() a 80 byte buffer, which will contain all 3 strings (asuming you've fixed issue 1). But since you write one byte more than the string is long, you'll have a zero byte in the middle of your readbuffer. Any attempt to print that will simply stop at that zero byte.
It'll be important to add error handling. You can never ever assume that a read or write will be successful.
I've modified your code a little, such that it works better (but not right yet):
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
int main(void)
{
int fd[2], nbytes;
pid_t childpid;
/* added newlines to separate the entries when printing */
char string[3][10] = {
"spike\n",
"tom\n",
"jerry\n"
};
char readbuffer[80];
pipe(fd);
if((childpid = fork()) == -1)
{
perror("fork");
exit(1);
}
if(childpid == 0)
{
/* Child process closes up input side of pipe */
close(fd[0]);
/* Send "string" through the output side of pipe */
/* Added a loop here, so all 3 entries are written */
for (int i = 0; i < 3; ++i) {
write(fd[1], string[i], (strlen(string[i])));
}
exit(0);
}
else
{
/* Parent process closes up output side of pipe */
close(fd[1]);
/* Read in a string from the pipe */
/* no loop needed here for now
But you'd need to read until you reach EOF.
I leave that as an exercise
*/
nbytes = read(fd[0], readbuffer, sizeof(readbuffer));
readbuffer[nbytes] = '\0';
printf("Received string: %s \n", readbuffer);
}
return(0);
}