popen2は新しくプログラムを起動してその入出力を奪う。どこかのサイトからのこぴぺなんだけど失念してしまいました。

popen2.cpp

#include <unistd.h>
#include <netdb.h>
#include <dirent.h>
#include <fcntl.h>
#include <signal.h>
 
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <sys/param.h>
#include <sys/ioctl.h>
 
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
#include <fstream>
#include <iostream>
#include <string>
#include <map>
 
#define R 0
#define W 1
 
char pipebuf[0x1000];
 
int popen2(const char *command, int *pfd){
  int pipe_c2p[2], pipe_p2c[2];
  pid_t pid;
 
  if(pipe(pipe_c2p) < 0){
    perror("popen2");
    return -1;
  }
 
  if(pipe(pipe_p2c) < 0){
    perror("popen2");
    close(pipe_c2p[R]), close(pipe_c2p[W]);
    return -1;
  }
 
  if((pid = fork()) < 0){
    perror("popen2");
    close(pipe_c2p[R]), close(pipe_c2p[W]);
    close(pipe_p2c[R]), close(pipe_p2c[W]);
    return -1;
  }
 
  if(pid == 0){
    close(pipe_p2c[W]), close(pipe_c2p[R]);
    dup2(pipe_p2c[R], STDIN_FILENO);
    dup2(pipe_c2p[W], STDOUT_FILENO);
    close(pipe_p2c[R]), close(pipe_c2p[W]);
    if(execlp("sh", "sh", "-c", command, NULL) < 0){
      perror("popen2");
      close(pipe_p2c[R]), close(pipe_c2p[W]);
      exit(-1);
    }
  }
 
  close(pipe_p2c[R]), close(pipe_c2p[W]);
  pfd[R] = pipe_c2p[R];
  pfd[W] = pipe_p2c[W];
 
  return pid;
}