system, fileExist函数包装

#include "stdio.h"
#include <string>
#include<sys/types.h>
#include<fcntl.h> 
#include <sys/stat.h>
using std::string;

#include <iostream>
#include <map>
#include <string>
#include <sys/time.h>
#include <errno.h>
#include <iconv.h>
#include <stdlib.h>
#include <stdarg.h>
#include <sys/select.h>
#include <sys/time.h>

string System(string &strrtn, const char *cpFormat, ...)
{
    if (cpFormat == NULL)
        return strrtn;

    char cpcmd[409600];
    char cpline[1024];
    FILE *fp;
    va_list val;

    va_start(val, cpFormat);
    vsnprintf(cpcmd, sizeof(cpcmd)-1, cpFormat, val);
    va_end(val);

    fp = popen(cpcmd, "r");

    while (fgets(cpline, 1023, fp) != NULL)
    {
        strrtn += cpline;
    }
    pclose(fp);
    return strrtn;
}

bool fileExist(const char *cpfile)
{
    if (NULL == cpfile)
        return false;

    struct stat st;
    if (stat(cpfile, &st) == -1)                                                                                                  
        return false; 

    return (!( st.st_mode & S_IFDIR));
}


int fileSize(const char *cpfilename)
{
    struct stat st;

       // 须处理符号链接文件
    if (stat(cpfilename, &st) != 0)
        return -1;
    return st.st_size;
}

int main(int argc, char*argv[])
{
    string arg = argv[1];
    string fileName = arg;
    string path = "";
    string file = path + fileName;

    int size = fileSize(file.c_str());
    
    if(!fileExist(file.c_str()))
    {
        printf("The file not exists! name: %s size: %d \n", file.c_str(), size);
    }
    else
    {
        printf("file exists! name: %s size: %d\n", file.c_str(), size);
    }


    int fd = open(file.c_str(), O_RDONLY);
    if(fd == -1)
    {
        printf("can not open file: %d\n", fd);
    }
    else
    {
        printf("open file %d\n", fd);
    }

    string calsize = "ls -l " + fileName + " | awk '{print $5}'";
    string val;
    val = System(val, calsize.c_str());
    if(val.size() != 0)
    {
        printf("size is %d\n", atoi(val.c_str()));
    }
    else
    {
        printf("error\n");
    }
    return 0;
}