Sending image through pipe to child process in C - c

Question

What my program needs to do is create child process, then transform it into dipslay program and send a PNG image through a pipe to it. I think i'm close, but i don't know how to send an image through pipe.
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <string.h>
int main(void)
{
int fd[2];
pid_t childpid;
char string[] = "";
char readbuffer[10000];
char buf[10000];
FILE *fptr;
pipe(fd);
if((childpid = fork()) == -1)
{
perror("fork");
exit(1);
}
if(childpid == 0)
{
//Child
close(fd[1]);
dup(fd[0]);
execl("/usr/bin/display","display", (char *)0);
read(fd[0], readbuffer, sizeof(readbuffer));
exit(0);
}
else
{
//Parent
close(fd[0]);
dup2(fd[1],1);
printf("Type name of the file:\n");
scanf("%s",string);
fptr = fopen(string, "r");
while ( fgets(buf, sizeof(buf), fptr) != NULL) {
write(fd[1], buf, strlen(buf));
}
fclose(fptr);
}
return(0);

Answer 1

Firstly you need to close the file descriptor associated with standard input.
close(0);
then duplicate fd[0]. It should work. You don't need to duplicate fd[1] in parent process.
My program:
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
int main()
{
int pipe_fd[2];
int c;
FILE *file;
pipe(pipe_fd);
if(fork()==0)
{
//child
close(pipe_fd[1]);
close(0);
dup(pipe_fd[0]);
execl("/usr/bin/display","display", (char*)NULL);
read(pipe_fd[0], &c, 1);
exit(1);
}
// parent
close(pipe_fd[0]);
file=fopen("Lena2.pgm","r");
if(file==NULL)
printf("File error\n");
while(!feof(file))
{
c=getc(file);
write(pipe_fd[1], &c, 1);
}
}