C/C++中判斷某一文件或目錄是否存在
1.C++很簡單的一種辦法：
#include <iostream>
#include <fstream>
using namespace std;
#define FILENAME "stat.dat"
int main()
{
fstream _file;
_file.open(FILENAME,ios::in);
if(!_file)
{
cout<<FILENAME<<"沒有被創建";
}
else
{
cout<<FILENAME<<"已經存在";
}
return 0;
}
2.利用 c 語言的庫的辦法：
函數名:
access
功 能: 確定文件的訪問權限
用 法: int access(const char *filename, int amode);
以前一直沒用過這個函數,今天調試程序發現了這個函數,感覺挺好用,尤其是判斷一個文件或文件夾是否存在的時候,用不着再find了,文件的話還可以檢測讀寫權限,文件夾的話則只能判斷是否存在,下面摘自MSDN：
int _access( const char *path, int mode );
Return Value
Each of these functions returns 0 if the file has the given mode. The function returns –1 if the named file does not exist or is not accessible in the given mode; in this case, errno is set as follows:
EACCES
Access denied: file’s permission setting does not allow specified access.
ENOENT
Filename or path not found.
Parameters
path
File or directory path
mode
Permission setting
Remarks
When used with files, the _access function determines whether the specified file exists and can be accessed as specified by the value of mode. When used with directories, _access determines only whether the specified directory exists; in Windows NT, all directories have read and write access.
mode
Value Checks
File For
00
Existence only
02
Write permission
04
Read permission
06
Read and write permission
Example
/* ACCESS.C: This example uses _access to check the
* file named "ACCESS.C" to see if it exists and if
* writing is allowed.
*/
#include <io.h>
#include <stdio.h>
#include <stdlib.h>
void main( void )
{
/* Check for existence */
if( (_access( "ACCESS.C", 0 )) != -1 )
{
printf( "File ACCESS.C exists
" );
/* Check for write permission */
if( (_access( "ACCESS.C", 2 )) != -1 )
printf( "File ACCESS.C has write permission
" );
}
}
Output
File ACCESS.C existsFile ACCESS.C has write permission
3.在windows平臺下用API函數FindFirstFile(...):
(1)檢查文件是否存在:
#define _WIN32_WINNT 0x0400
#include "windows.h"
int
main(int argc, char *argv[])
{
WIN32_FIND_DATA FindFileData;
HANDLE hFind;
printf ("Target file is %s.
", argv[1]);
hFind = FindFirstFile(argv[1], &FindFileData);
if (hFind == INVALID_HANDLE_VALUE) {
printf ("Invalid File Handle. Get Last Error reports %d
", GetLastError ());
} else {
printf ("The first file found is %s
", FindFileData.cFileName);
FindClose(hFind);
}
return (0);
}
(2)檢查某一目錄是否存在：
///目錄是否存在的檢查：
bool CheckFolderExist(const string &strPath)
{
WIN32_FIND_DATA wfd;
bool rValue = false;
HANDLE hFind = FindFirstFile(strPath.c_str(), &wfd);
if ((hFind != INVALID_HANDLE_VALUE) && (wfd.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY))
{
rValue = true;
}
FindClose(hFind);
return rValue;
}
4.使用boost的filesystem類庫的exists函數
#include <boost/filesystem/operations.hpp>
#include <boost/filesystem/path.hpp>
#include <boost/filesystem/convenience.hpp>
int GetFilePath(std::string &strFilePath)
{
string strPath;
int nRes = 0;
//指定路徑
strPath = "D:/myTest/Test1/Test2";
namespace fs = boost::filesystem;
//路徑的可移植
fs::path full_path( fs::initial_path() );
full_path = fs::system_complete( fs::path(strPath, fs::native ) );
//判斷各級子目錄是否存在，不存在則需要創建
if ( !fs::exists( full_path ) )
{
// 創建多層子目錄
bool bRet = fs::create_directories(full_path);
if (false == bRet)
{
return -1;
}
}
strFilePath = full_path.native_directory_string();
return 0;
}