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C/C++中如何判斷某一文件或目錄是否存在
不同的編程語(yǔ)言判斷文件是否存在的方法是不一樣的。你知道C/C++中如何判斷某一文件或目錄是否存在嗎?下面是小編為大家?guī)?lái)的C/C++中如何判斷某一文件或目錄是否存在的知識(shí)，歡迎閱讀。
1.C++很簡(jiǎn)單的一種辦法：
復(fù)制代碼 代碼如下:
#include
#include
using namespace std;
#define FILENAME "stat.dat"
int main()
{
fstream _file;
_file.open(FILENAME,ios::in);
if(!_file)
{
cout<
}
else
{
cout<
}
return 0;
}
2.利用 c 語(yǔ)言的庫(kù)的辦法：
函數(shù)名: access
功 能: 確定文件的訪問(wèn)權(quán)限
用 法: int access(const char *filename, int amode);
以前一直沒(méi)用過(guò)這個(gè)函數(shù),今天調(diào)試程序發(fā)現(xiàn)了這個(gè)函數(shù),感覺(jué)挺好用,尤其是判斷一個(gè)文件或文件夾是否存在的時(shí)候,用不著再find了,文件的話還可以檢測(cè)讀寫(xiě)權(quán)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
復(fù)制代碼 代碼如下:
/* ACCESS.C: This example uses _access to check the
* file named "ACCESS.C" to see if it exists and if
* writing is allowed.
*/
#include
#include
#include
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 " );
}
}
OutputFile ACCESS.C existsFile ACCESS.C has write permission
3.在windows平臺(tái)下用API函數(shù)FindFirstFile(...):
(1)檢查文件是否存在:
復(fù)制代碼 代碼如下:
#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：
復(fù)制代碼 代碼如下:
///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(kù)的exists函數(shù)
復(fù)制代碼 代碼如下:
#include
#include
#include
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(jí)子目錄是否存在，不存在則需要?jiǎng)?chuàng)建
if ( !fs::exists( full_path ) )
{
// 創(chuàng)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;
}
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