现在在C中管道IPC

Question

For self learning prupose I want to connect 2 programms with pipes. The first program takes input, makes it upper and print to screen, in this example first program gets executed but no input output possible. How I have to change the pipe close() functions in second program to get a result.

Answer 1

Close output pipe right after writing or modify your first program to fflush(stdout) after each character write (because of buffering nature of std(in|out) second program stucks on read and first program waits for input as it didn't get EOF - close() from second program sends EOF to first, first one terminates and on termination stdout is flushed automatically).

int main(int argc, char** argv) {
  pid_t pid;
  int fi[2];
  int fo[2];

  char c;

  if (pipe(fi) < 0)
    perror("pipe");
  if (pipe(fo) < 0)
    perror("pipe");

  switch ( fork() ) {
  case -1:
    exit(1);
  case 0:
    dup2(fi[0], STDIN_FILENO);
    close(fi[1]);
    dup2(fo[1], STDOUT_FILENO);
    close(fo[0]);
    execlp("pipes1", "pipes1",(char *)NULL);

  default:
    close(fi[0]);
    close(fo[1]);
    break;
  }

  write(fi[1], "t", 1);
  close(fi[1]);
  read(fo[0], &c, 1);
  printf("%c\n", c);
  close(fo[0]);

  return 0;
}