システムプログラミング：プロセス間通信(pipe利用)

親プログラムで入力したものを、子プログラムを処理し親プログラムに返す

[parent.c]

#include <stdio.h>

#include <stdlib.h>

#include <="" span="">types.h>

#include <="" span="">wait.h>

#include <unistd.h> 

int main(){
  char line[32];
  char read_fd[3], write_fd[3];
  int number, result;
  int fd[2];
  int st;
  if (pipe(fd) <0){
    perror("pipe");
    exit (EXIT_FAILURE);
  }

  snprintf (read_fd, sizeof (read_fd),"%d", fd[0]);
  snprintf (write_fd, sizeof (write_fd),"%d", fd[1]);
  fgets (line, sizeof (line), stdin);
  if (sscanf (line,"%d", &number) >0){
    if (fork () == 0){
      if (execl ("child", "child", read_fd, write_fd, NULL) <0){
        exit (EXIT_FAILURE);
      }
    }
    write (fd[1], &number, sizeof (number));
    wait (&st);
    read (fd[0], &result, sizeof (result));
    printf ("%d x %d = %d\n", number, number, result);
    close (fd[0]);
    close (fd[1]);
  }
  return EXIT_SUCCESS;
}

[child.c]
#include <stdlib.h>


#include <unistd.h>
int main (int argc, char *argv[]){
  int number, result;
  int read_fd, write_fd;
  //　引数の文字列を整数に変換
  read_fd = atoi (argv[1]);
  write_fd = atoi (argv[2]);
  //　パイプラインからデータを読み込む
  read (read_fd, &number, sizeof (number));
  result = number*number;
  //　パイプラインにデータを書き込む
  write (write_fd, &result, sizeof (result));
  close (read_fd);
  close (write_fd);
  return EXIT_SUCCESS;
}

atmark@atde3:~/Desktop/work$ ./parent
3
3 x 3 = 9＼natmark@atde3:~/Desktop/work$