I'm writing a coprocess program using pipe. It works fine when the child read some data, handle it and output it. But when I read all the data and handle it, it just pending. Any body have some idea? Thank you.

Here is the source code:

```
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>

int main()
{
    #define MAXSIZE 1024

    char workload[MAXSIZE];
    char result[MAXSIZE];
    workload[strlen(workload)] = EOF;
    int workload_size = strlen(workload);

    int fd1[2], fd2[2];
    int n;
    pid_t pid;
    if (pipe(fd1) < 0 || pipe(fd2) < 0) {
        fprintf(stderr, "pipe error: %s\n", strerror(errno));
        exit(1);
    }

    if ((pid = fork()) < 0) {
        fprintf(stderr, "fork error: %s\n", strerror(errno));
        exit(1);
    } else if (pid > 0) {
        close(fd1[0]);
        close(fd2[1]);
        while(fgets(workload, MAXSIZE, stdin) != NULL)
        {
            workload_size = strlen(workload);
            if (write(fd1[1], workload, workload_size) != workload_size) {
                fprintf(stderr, "write to pipe error: %s\n", strerror(errno));
                exit(1);
            }

            if ((n = read(fd2[0], result, MAXSIZE)) < 0) {
                fprintf(stderr, "read from pipe error: %s\n", strerror(errno));
                exit(1);
            }

            if (n == 0) {
                fprintf(stderr, "child closed the pipe\n");
                exit(1);
            }

            result[n] = 0;

            if (puts(result) == EOF) {
                fprintf(stderr, "fputs error\n");
                exit(1);
            }
        }
    } else {
        close(fd1[1]);
        close(fd2[0]);
        if (fd1[0] != STDIN_FILENO) {
            if (dup2(fd1[0] ,STDIN_FILENO) != STDIN_FILENO) {
                fprintf(stderr, "dup2 error to stdin.\n");
                exit(1);
            }
            close(fd1[0]);
        }
        if (fd2[1] != STDOUT_FILENO) {
            if (dup2(fd2[1] ,STDOUT_FILENO) != STDOUT_FILENO) {
                fprintf(stderr, "dup2 error to stdout.\n");
                exit(1);
            }
            close(fd2[1]);
        }

        if (execl("./a.out", "a.out", NULL) < 0) {
            fprintf(stderr, "execl error: %s\n", strerror(errno));
            exit(1);
        }
        exit(0);
    }

    return 0;
}

```

Here is the source code of a.out, it works well with this:

```
#include <stdio.h>
#include <string.h>

int main()
{
    #define MAXSIZE 1024
    char x[MAXSIZE];
    int n;
    while(scanf("%s", x) != EOF)
    {
        printf("len:%d %s", strlen(x), x);
        fflush(stdout);
    }
    return 0;
}

```

But it seems just pending when I write the code like this:

```
#include <stdio.h>
#include <string.h>

int main()
{
    #define MAXSIZE 1024
    char x[MAXSIZE];
    int n;
    while(scanf("%s", x) != EOF);
    printf("Ok\n");
    fflush(stdout);

    return 0;
}

```