PipedForks03.cpp

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <iostream>

#define PIPE_READ 0
#define PIPE_WRITE 1

std::string createChild(const char* bashCmd)
{
    int aStdinPipe[2];
    int aStdoutPipe[2];
    int nChild;
    int nResult;
    char buffer[4096];
    std::string commandResult;
    if(pipe(aStdinPipe) < 0)
    {
        exit(1);
    }
    if(pipe(aStdoutPipe) < 0)
    {
        close(aStdinPipe[PIPE_READ]);
        close(aStdinPipe[PIPE_WRITE]);
        exit(1);
    }
    nChild = fork();
    if(0 == nChild)
    {
        if(dup2(aStdinPipe[PIPE_READ], STDIN_FILENO) == -1)//redirect stdin
        {
            exit(1);
        }
        if(dup2(aStdoutPipe[PIPE_WRITE], STDOUT_FILENO) == -1)
        {
            exit(1);
        }
        close(aStdinPipe[PIPE_READ]);
        close(aStdinPipe[PIPE_WRITE]);
        close(aStdoutPipe[PIPE_READ]);
        close(aStdoutPipe[PIPE_WRITE]);
        nResult = execl("/bin/bash", "bash", "-c", bashCmd, (char*)0);
        exit(nResult);
    }
    else if(nChild > 0)
    {
        close(aStdinPipe[PIPE_READ]);
        close(aStdoutPipe[PIPE_WRITE]);
        memset(buffer, 0, sizeof(buffer));
        read(aStdoutPipe[PIPE_READ], buffer, sizeof(buffer));
        commandResult = buffer;
        close(aStdinPipe[PIPE_WRITE]);
        close(aStdoutPipe[PIPE_READ]);
    } else
    {
        close(aStdinPipe[PIPE_READ]);
        close(aStdinPipe[PIPE_WRITE]);
        close(aStdoutPipe[PIPE_READ]);
        close(aStdoutPipe[PIPE_WRITE]);
    }
    return commandResult;
}

int main(void)
{
    std::cout<<"CommandReturns : "<<createChild("ls -hal")<<std::endl;//"echo \"test\""
    std::cout<<"CommandBReturns : "<<createChild("echo \"test\"")<<std::endl;
    return 0;
}