#include <stdio.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <fcntl.h>
int main (int argc, char *argv[])
{
    if (argc != 2)
    {
        printf("Blad argumentow\n");
        return 1;
    }

    int fds[2];
    pid_t pid;

    /* Create a pipe. File descriptors for the two ends of the pipe are placed in fds. */
    /* TODO add error handling for system calls like pipe, fork, etc. */
    if(pipe (fds) == -1)
    {
        printf("Pipe error\n");
        return 1;
    }

    /* Fork a child process. */
    pid = fork ();

    if (pid < 0)
    {
        return 1;
    }

    if (pid == (pid_t) 0)
    {
    /* This is the child process. Close our copy of the write end of the file descriptor. */
    close (fds[1]);
    /* Connect the read end of the pipe to standard input. */
    dup2 (fds[0], STDIN_FILENO);
    int file_desc = open(argv[1],O_WRONLY|O_TRUNC|O_CREAT,0600);
    dup2 (file_desc, STDOUT_FILENO);
    /* Replace the child process with the "sort” program. */
    execlp ("sort", "sort", NULL);
    }

    else
    {
        /* This is the parent process. */
        FILE* stream;
        /* Close our copy of the read end of the file descriptor. */
        close (fds[0]);
        /* Convert the write file descriptor to a FILE object, and write to it. */
        stream = fdopen (fds[1], "w");
    if (stream == NULL)
    {
        fprintf(stderr, "Blad otwarcia strumienia\n");
        return 1;
    }
        fprintf (stream, "This is a test.\n");
        fprintf (stream, "Hello, world.\n");
        fprintf (stream, "My dog has fleas.\n");
        fprintf (stream, "This program is great.\n");
        fprintf (stream, "One fish, two fish.\n");
        fflush (stream);
        close (fds[1]);
        /* Wait for the child process to finish. */
        waitpid (pid, NULL, 0);
    }
    return 0;
}