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C Pipe: parent to read from child to graduation

The code below shows how the child process can write to the end of the pipe , and then how the parent process can read from the other end, What I noticed after I experimented with the code is that only after as the child process is complete , the parent will be able to read the data.

Is there a way to make the parent process come to the fore and read the data right after the child calls write () ? And is there a way to read data without interrupting a child?

#include <stdio.h> /* For printf */
#include <string.h> /* For strlen */
#include <stdlib.h> /* For exit */

#define READ 0 /* Read end of pipe */
#define WRITE 1 /* Write end of pipe */
char *phrase = "This is a test phrase.";
main(){
    int pid, fd[2], bytes;
    char message[100];

    if (pipe(fd) == -1) { /* Create a pipe */
        perror("pipe"); 
        exit(1); 
    }
    if ((pid = fork()) == -1) { /* Fork a child */
        perror("fork"); 
        exit(1); 
    }
    if (pid == 0) { /* Child, writer */
        close(fd[READ]); /* Close unused end */
        write(fd[WRITE], phrase, strlen(phrase)+1);
        close(fd[WRITE]); /* Close used end */
    } 
    else { /* Parent, reader */
        close(fd[WRITE]); /* Close unused end */
        bytes = read(fd[READ], message, sizeof(message));
        printf("Read %d bytes: %s\n", bytes, message);
        close(fd[READ]);  /* Close used end */
    }
}
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4

. sleep(120) .

+2

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I also want the parent to read the data immediately after the child whites to
the pipe.

, ? .

#include <stdio.h> /* For printf */
#include <string.h> /* For strlen */
#include <stdlib.h> /* For exit */

#define READ 0 /* Read end of pipe */
#define WRITE 1 /* Write end of pipe */
char *phrase = "This is a test phrase.";
main(){
  int pid, fd[2], bytes;
  char message[100];
  int fd1[2];
  char buffer[1];
  int ret;

  if (pipe(fd) == -1) { /* Create a pipe */
    perror("pipe");
    exit(1);
  }
  if (pipe(fd1) == -1) { /* Create a pipe */
    perror("pipe");
    exit(1);
  }
  if ((pid = fork()) == -1) { /* Fork a child */
    perror("fork");
    exit(1);
  }
  if (pid == 0) { /* Child, writer */
    close(fd[READ]); /* Close unused end */
    close(fd1[WRITE]);/*Close write  end of the 2nd pipe*/
    write(fd[WRITE], phrase, strlen(phrase)+1);
    close(fd[WRITE]); /* Close used end */
    /*For synchronisation let the child try to
    read from the 2nd pipe. 
    The function read, will return 0 only when the
    parent terminates and in this we are
    not interested if at all anything read or not.
    The read statement below, will return only if the
    parent has terminated, thus ensures that the
    child terminates only after the parent*/
    ret = read(fd1[READ],buffer, 1);
  }

else { /* Parent, reader */
    close(fd[WRITE]); /* Close unused end */
    close(fd1[READ]); /*Close read end of the 2nd pipe*/
    bytes = read(fd[READ], message, sizeof(message));
    printf("Read %d bytes: %s\n", bytes, message);
    close(fd[READ]);  /* Close used end */

   }
}
+1

fd [0] = 0 fd [1] = 0

0

, pipe pipe. .

#include <stdio.h> /* For printf */
#include <string.h> /* For strlen */
#include <stdlib.h> /* For exit */

#define READ 0 /* Read end of pipe */
#define WRITE 1 /* Write end of pipe */
char *phrase = "This is a test phrase.";
main(){
    int pid, fd[2], bytes;
    char message[100];

    if (pipe(fd) == -1) { /* Create a pipe */
        perror("pipe"); 
        exit(1); 
    }
    if ((pid = fork()) == -1) { /* Fork a child */
        perror("fork"); 
        exit(1); 
    }
    if (pid == 0) { /* Child, writer */
        close(fd[READ]); /* Close unused end */
        write(fd[WRITE], phrase, strlen(phrase)+1);
        sleep(10);
        close(fd[WRITE]); /* Close used end */
        sleep(20);
    } 
    else { /* Parent, reader */
        printf( "child ipd = %d\n\r", pid);
        close(fd[WRITE]); /* Close unused end */
        bytes = read(fd[READ], message, sizeof(message));
        printf("Read %d bytes: %s\n", bytes, message);
        close(fd[READ]);  /* Close used end */
        sleep(10);
    }
}
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