C/C++中判断某一文件或目录是否存在

C/C++中判断某一文件或目录是否存在

1.C++很简单的一种办法：

#include <iostream>

#include <fstream>

using namespace std;

#define FILENAME "stat.dat"

int main()

{

fstream _file;

_file.open(FILENAME,ios::in);

if(!_file)

{

cout<<FILENAME<<"没有被创建";

}

else

{

cout<<FILENAME<<"已经存在";

}

return 0;

}

2.利用 c 语言的库的办法：
函数名: access

功 能: 确定文件的访问权限

用 法: int access(const char *filename, int amode);

以前一直没用过这个函数,今天调试程序发现了这个函数,感觉挺好用,尤其是判断一个文件或文件夹是否存在的时候,用不着再find了,文件的话还可以检测读写权限,文件夹的话则只能判断是否存在,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 " );
}
}
[/code]

Output[/code]

File ACCESS.C existsFile ACCESS.C has write permission

3.在windows平台下用API函数FindFirstFile(...):

(1)检查文件是否存在:

#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)检查某一目录是否存在：

///目录是否存在的检查：

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类库的exists函数

#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;

//指定路径

strPath = "D:/myTest/Test1/Test2";

namespace fs = boost::filesystem;

//路径的可移植

fs::path full_path( fs::initial_path() );

full_path = fs::system_complete( fs::path(strPath, fs::native ) );

//判断各级子目录是否存在，不存在则需要创建

if ( !fs::exists( full_path ) )

{

// 创建多层子目录

bool bRet = fs::create_directories(full_path);

if (false == bRet)

{

return -1;

}

}

strFilePath = full_path.native_directory_string();

return 0;

}