WinAPI FileExists Function Implemetation - c++

I am coding a simple replacement for std::filesystem::exists() function using Windows API. Surprisingly, it turned out to be pretty hard. I want to keep my code simple, so I am using minimum functions. My function of choice is GetFileAttributesW(). Code is tested with fs::recursive_directory_iterator() function. My function thinks that all files in “C:\Windows\servicing\LCU*” don’t exist (ERROR_PATH_NOT_FOUND). This directory is responsible for storing Windows Update Caches and is famous for having extremely long file names. I couldn’t find anything else about this directory. Example of filenames and my code are included below. Hope this helps!
Edited:
The solution to this problem is to prepend absolute file path with “\\?\” char sequence. It makes Windows handle short files correctly!
C:\Windows\servicing\LCU\Package_for_RollupFix~31bf3856ad364e35~amd64~~19041.2006.1.7\amd64_microsoft-windows-a..g-whatsnew.appxmain_31bf3856ad364e35_10.0.19041.1741_none_ee5d4a8d060d7653\f\new360videossquare44x44logo.targetsize-16_altform-unplated_contrast-black.png
C:\Windows\servicing\LCU\Package_for_RollupFix~31bf3856ad364e35~amd64~~19041.2006.1.7\amd64_microsoft-windows-a..g-whatsnew.appxmain_31bf3856ad364e35_10.0.19041.1741_none_ee5d4a8d060d7653\f\new360videossquare44x44logo.targetsize-16_altform-unplated_contrast-white.png
C:\Windows\servicing\LCU\Package_for_RollupFix~31bf3856ad364e35~amd64~~19041.2006.1.7\amd64_microsoft-windows-a..g-whatsnew.appxmain_31bf3856ad364e35_10.0.19041.1741_none_ee5d4a8d060d7653\f\new360videossquare44x44logo.targetsize-20_altform-unplated_contrast-black.png
C:\Windows\servicing\LCU\Package_for_RollupFix~31bf3856ad364e35~amd64~~19041.2006.1.7\amd64_microsoft-windows-a..g-whatsnew.appxmain_31bf3856ad364e35_10.0.19041.1741_none_ee5d4a8d060d7653\f\new360videossquare44x44logo.targetsize-20_altform-unplated_contrast-white.png
#include <windows.h>
#include <filesystem>
#include <iostream>
#include <string>
using namespace std;
namespace fs = std::filesystem;
int FileExists(wstring file_path) {
/* TODO:
1. Doesn't work with "C:\\Windows\\servicing\\LCU\\*".
2. Improve error system.
*/
DWORD attributes = GetFileAttributesW(file_path.c_str());
// Valid attributes => File exists
if (attributes != INVALID_FILE_ATTRIBUTES) {
return true;
}
DWORD error_code = GetLastError();
wcout << error_code << ' ' << file_path << '\n';
// Path related error => File doesn't exist
if (error_code == ERROR_PATH_NOT_FOUND || error_code == ERROR_INVALID_NAME ||
error_code == ERROR_FILE_NOT_FOUND || error_code == ERROR_BAD_NETPATH)
{
return false;
}
// Other errors are logged before if statement
// File is busy with IO operations, etc.
return error_code;
}
int main() {
for (fs::path path : fs::recursive_directory_iterator("C:\\", fs::directory_options::skip_permission_denied)) {
FileExists(path);
}
return 0;
}

The solution that worked for me is to prepend absolute file path with “\\?\” char sequence. Somehow, it makes Windows handle shortened file paths correctly!
Check out MSDN Article "Maximum File Path Limitation" for more info.

Related

This breakpoint will not be hit

I looked at numerous posts concerning this problem but none of them apply in my case.
I have a C++ class in one file that has 3 methods. I can set a breakpoint in one method. However, I cannot set a breakpoint on any line of code in the other two methods. This class is build as a library with DEBUG set. All optimizations are turned off.
Below is the code for the two problem methods in this class.
Blockquote
#include "pch.h"
#include <stdio.h>
#include <afxwin.h>
#include <cstring>
#include <io.h>
#include <iostream>
#include <string>
#include "Log.h"
CLog::CLog()
{
ptLog = NULL; // this is the file ptr
}
void CLog::Init()
{
int iFD;
DWORD iLength;
int iStat;
HMODULE hMod;
std::string sPath;
std::string sFile;
int i;
hMod = GetModuleHandle(NULL); // handle to this execuatble
std::cout << "Module = " << hMod;
if(hMod)
{
// Use two bytes ASCII (UNICODE) if set by compiler
char acFile[120];
// Full path name of exe file
GetModuleFileName(hMod, acFile, sizeof(acFile));
std::cout << "File Name = " << acFile<<"\n";
// extract file name from full path and append .log
sPath = acFile;
i = sPath.find_last_of("\\/");
sFile = sPath.substr(i + 1);
sFile.copy(acFile, 120);
std::cout << " File Name Trunc = " << sFile;
sFile.append(".log");
iStat = fopen_s(&ptLog, sFile.data(), "a+"); // append log data to file
std::cout << "fopen stat = " << iStat;
if (iStat != 0) // failed to open error log
{
return;
}
iFD = _fileno(ptLog);
iLength = _filelength(iFD);
// Check length. If too large rename and create new file.
if (iLength > MAX_LOG_SIZE)
{
fclose(ptLog);
char acBakFile[80];
strcpy_s(acBakFile, 80, acFile);
strcat_s(acBakFile, ".bak"); // new name of old log file
remove(acBakFile); // remove previous bak file if it exists
rename(acFile, acBakFile);
fopen_s(&ptLog, acFile, "a+"); // Create new log file
}
}// end if (hMod)
}
,,,
ptLog is declared as FILE *
This class is invoked with the following code:
#include <iostream>
#include "..\Log\Log.h"
int main()
{
CLog Logger;
Logger.Init();
Logger.vLog((char *) "Hello \n");
}
Blockquote
This code is also compiled as debug. If a set a breakpoint on "Loggger.Init()"
the debugger will hit the breakpoint. If select 'Step Into' it will not enter
the code in the Init() method. The code does execute since I can see the text on the console. If I put breakpoints anywhere in the Init() method they do not break.
I did the following:
Removed log.lib from the input to the Linker.
Obviously, the Link failed due to unresolved externals.
Put back log.lib and rebuilt.
Turned off the option "Require source files that exactly match the original version"
Debug and breakpoints worked.
Enabled the option.
Retried debug and the breakpoints still worked.
Did a full rebuild and breakpoints worked.
I don't really understand it because I had performed numerous cleans and rebuilds
previously.
I did find another issue. I had '/clr' option on.
This is for Common Language Runtime support for the .lib.
The module linked to it did not have Common Language Runtime on. In this case,
the breakpoints were ignored. When I turned off '/ clr', the breakpoints
functioned properly

Creating folders in C++

I have recently started working in C++ and came across this situation when I have to create a directory while executing my code. The code is working fine when I have to create a single folder but it fails when I have to create another folder withing this newly created folder.
Suppose, I am in C: and want to store my file in C:/A/B/ .The following piece of code using mkdir() works fine if I have to store my file in C:/A/ but fails when I am adding another folder B.
Following is my code snippet:
#include <sys/stat.h>
#include <string>
using namespace std;
int main()
{
string stringpath = "C:/A/B/";
int status = mkdir(stringpath.c_str(),0777);
if(status!=0)
{
//.....
}
else
{
//....
}
}
Can someone help me in creating this directory where I can have any number of folders inside the parent directory? (P.S:I have added the header files sys/stat.h,iostream and string)
This is how you do it in C++17:
#include <filesystem>
namespace fs = std::filesystem;
fs::create_directories("./a/b/c")
mkdir() creates only the last component of the specified path. In your example, it will create only B. If any of the parent directories do not exist (ie, if A does not exist), the function fails with ENOENT. You need to split up the path and call mkdir() for every intermediate directory in the path, ignoring EEXIST errors as you go.
status = mkdir("C:/A/", 0777);
if ((status < 0) && (errno != EEXIST)) ...
status = mkdir("C:/A/B/", 0777);
if ((status < 0) && (errno != EEXIST)) ...
If you don't want to handle this manually, use a wrapper that handles it for you, such as Boost's create_directories() function:
bool create_directories(const path& p);
bool create_directories(const path& p, system::error_code& ec);
Effects: Establishes the postcondition by calling create_directory() for any element of p that does not exist.
Postcondition: is_directory(p)
Returns: true if a new directory was created, otherwise false.
Throws: As specified in Error reporting.
Complexity: O(n+1)where n is the number of elements of p that do not exist.
You can call the following:
string stringpath = "C:/A/B/";
int status = mkdir(stringpath.c_str(),0777);
If
C:/A/ directory exists. If its not exists, then do the following:
string stringpath = "C:/A/";
int status = mkdir(stringpath.c_str(),0777);
stringpath = "C:/A/B/";
int status = mkdir(stringpath.c_str(),0777);
In C++11 you can use the experimental functios:
#include <experimental/filesystem>
...
std::stringstream bufH;
bufH << dirName << fName;
if (!std::experimental::filesystem::exists(bufH.str()))
{
std::experimental::filesystem::create_directories(bufH.str());
}
Try the octal flag 7777 like this to have all the rights necessary to create this folder.
int status = mkdir(stringpath.c_str(), 7777);
Or do a chmod in the A folder like that :
chmod -r 7777 *

Search for path of .exe

So I'm looking for a piece of code that allows me to search for the path of the file it's being executed in. For example, I'm doing an autorun program for use in pendrives (example) but I don't know if it'll end up as D:, F:, G: or whatever so the program would search it's own path and open another file based on the path he is found using some 'if' statements.
Here's what I thought:
#include <stdlib.h>
#include <iostream>
using namespace std;
int main () {
// Insert 'search path' code and needed variables here.
if (-ThePath- == "d:\\AutoRun.exe")
{
system ("d:\\MyFolder\\OtherProgram.exe");
}
else if (-ThePath- == "f:\\AutoRun.exe")
{
system ("f:\\MyFolder\\OtherProgram.exe");
}
else if (-ThePath- == "g:\\AutoRun.exe")
{
system ("g:\\MyFolder\\OtherProgram.exe");
}
else
{
cout << "An error ocurred.\n";
cout << "Press enter to exit...\n";
cin.get();
};
return 0;
}
Is there some way this could be done?
GetModuleFileName : documentation here
EDITED - Pedro, the sample code from Microsoft handles a lot of things. To get the file path, all you need is :
TCHAR szPath[MAX_PATH];
if( !GetModuleFileName( NULL, szPath, MAX_PATH ) ) {
// handle error in GetModuleFileName
} else {
// now, szPath contains file path
};
In standard C++ argv[0] contains the name of the executable. For a program invoked in the normal way this will be the path of the executable on Windows.

C++ - Determining if directory (not a file) exists in Linux [duplicate]

This question already has answers here:
Checking if a directory exists in Unix (system call)
(5 answers)
Closed 4 years ago.
How would I determine if a directory (not a file) existed using C++ in Linux? I tried using the stat() function but it returned positive when a file was found. I only want to find if the inputted string is a directory, not something else.
According to man(2) stat you can use the S_ISDIR macro on the st_mode field:
bool isdir = S_ISDIR(st.st_mode);
Side note, I would recommend using Boost and/or Qt4 to make cross-platform support easier if your software can be viable on other OSs.
how about something i found here
#include <dirent.h>
bool DirectoryExists( const char* pzPath )
{
if ( pzPath == NULL) return false;
DIR *pDir;
bool bExists = false;
pDir = opendir (pzPath);
if (pDir != NULL)
{
bExists = true;
(void) closedir (pDir);
}
return bExists;
}
Or using stat
struct stat st;
if(stat("/tmp",&st) == 0)
if(st.st_mode & S_IFDIR != 0)
printf(" /tmp is present\n");
If you can check out the boost filesystem library. It's a great way to deal with this kind of problems in a generic and portable manner.
In this case it would suffice to use:
#include "boost/filesystem.hpp"
using namespace boost::filesystem;
...
if ( !exists( "test/mydir" ) ) {bla bla}
The way I understand your question is this: you have a path, say, /foo/bar/baz (baz is a file) and you want to know whether /foo/bar exists. If so, the solution looks something like this (untested):
char *myDir = dirname(myPath);
struct stat myStat;
if ((stat(myDir, &myStat) == 0) && (((myStat.st_mode) & S_IFMT) == S_IFDIR)) {
// myDir exists and is a directory.
}
In C++17**, std::filesystem provides two variants to determine the existence of a path:
is_directory() determines, if a path is a directory and does exist in the actual filesystem
exists() just determines, if the path exists in the actual filesystem (not checking, if it is a directory)
Example (without error handling):
#include <iostream>
#include <filesystem> // C++17
//#include <experimental/filesystem> // C++14
namespace fs = std::filesystem;
//namespace fs = std::experimental::filesystem; // C++14
int main()
{
// Prepare.
const auto processWorkingDir = fs::current_path();
const auto existingDir = processWorkingDir / "existing/directory"; // Should exist in file system.
const auto notExistingDir = processWorkingDir / "fake/path";
const auto file = processWorkingDir / "file.ext"; // Should exist in file system.
// Test.
std::cout
<< "existing dir:\t" << fs::is_directory(existingDir) << "\n"
<< "fake dir:\t" << fs::is_directory(notExistingDir) << "\n"
<< "existing file:\t" << fs::is_directory(file) << "\n\n";
std::cout
<< "existing dir:\t" << fs::exists(existingDir) << "\n"
<< "fake dir:\t" << fs::exists(notExistingDir) << "\n"
<< "existing file:\t" << fs::exists(file);
}
Possible output:
existing dir: 1
fake dir: 0
existing file: 0
existing dir: 1
fake dir: 0
existing file: 1
**in C++14 std::experimental::filesystem is available
Both functions throw filesystem_error in case of errors. If you want to avoid catching exceptions, use the overloaded variants with std::error_code as second parameter.
#include <filesystem>
#include <iostream>
namespace fs = std::filesystem;
bool isExistingDir(const fs::path& p) noexcept
{
try
{
return fs::is_directory(p);
}
catch (std::exception& e)
{
// Output the error message.
const auto theError = std::string{ e.what() };
std::cerr << theError;
return false;
}
}
bool isExistingDirEC(const fs::path& p) noexcept
{
std::error_code ec;
const auto isDir = fs::is_directory(p, ec);
if (ec)
{
// Output the error message.
const auto theError = ec.message();
std::cerr << theError;
return false;
}
else
{
return isDir;
}
}
int main()
{
const auto notExistingPath = fs::path{ "\xa0\xa1" };
isExistingDir(notExistingPath);
isExistingDirEC(notExistingPath);
}
If you want to find out whether a directory exists because you want to do something with it if it does (create a file/directory inside, scan its contents, etc) you should just go ahead and do whatever you want to do, then check whether it failed, and if so, report strerror(errno) to the user. This is a general principle of programming under Unix: don't try to figure out whether the thing you want to do will work. Attempt it, then see if it failed.
If you want to behave specially if whatever-it-was failed because a directory didn't exist (for instance, if you want to create a file and all necessary containing directories) you check for errno == ENOENT after open fails.
I see that one responder has recommended the use of boost::filesystem. I would like to endorse this recommendation, but sadly I cannot, because boost::filesystem is not header-only, and all of Boost's non-header-only modules have a horrible track record of causing mysterious breakage if you upgrade the shared library without recompiling the app, or even if you just didn't manage to compile your app with exactly the same flags used to compile the shared library. The maintenance grief is just not worth it.

how to search the computer for files and folders

i need a way to search the computer for files like Windows Explorer. i want my program to search lets say hard drive c:. i need it to search C:\ for folders and files (just the ones you could see in c:\ then if the user clicks on a file on the list like the folder test (C:\test) it would search test and let the user see what files/folders are in it.
Since you mentioned windows, the most straight forward winapi way to do it is with FindFirstFile and FindNextFile functions.
edit: Here's an example that shows you how to enumerate all files/folders in a directory.
#include <Windows.h>
#include <iostream>
int main()
{
WIN32_FIND_DATA file;
HANDLE search_handle=FindFirstFile(L"C:\\*",&file);
if (search_handle)
{
do
{
std::wcout << file.cFileName << std::endl;
}while(FindNextFile(search_handle,&file));
FindClose(search_handle);
}
}
This will be OS dependent. The SO question
How can I get a list of files in a directory using C or C++?
handles this problem well. You can download DIRENT here.
Now that you have this, I'd recommend recursively searching for a file with a DFS/BFS algorithm. You can assume the whole directory structure is a tree where each file is a leaf node and each subdirectory is an internal node.
So all you have to do is,
Get the list of files/folders in a directory with a function such as:
void getFilesFolders(vector<string> & dir_list, const string & folder_name)
If it's a directory, go to 1 with the directory name
If it's a file, terminate if it's the file you're looking for, else move on to the next file.
boost::filesystem can be a cross-platform solution for that (check out for such functions in it).
You can use Directory class members to do this with C# or managed C++. See the following MSDN article:
http://support.microsoft.com/kb/307009
If you wish to use C++ with MFC you can use CFileFind
http://msdn.microsoft.com/en-us/library/f33e1618%28v=VS.80%29.aspx
You'll have to supply your own browse window to present the file system tree.
Or you can use one of the directory/file controls to do both for you.
#include <Windows.h>
#include <iostream>
int FindF(char* pDirectory)
{
char szFindPath[MAX_PATH] = {0};
strcpy(szFindPath, pDirectory);
strcat(szFindPath, "\\*");
WIN32_FIND_DATA file;
HANDLE search_handle=FindFirstFile(szFindPath,&file);
if (search_handle)
{
do
{
if(file.dwFileAttributes == FILE_ATTRIBUTE_DIRECTORY)
{
strcpy(szFindPath, pDirectory);
strcat(szFindPath, "\\");
strcat(szFindPath, file.cFileName);
FindF(szFindPath);
}
std::wcout << file.cFileName << std::endl;
}while(FindNextFile(search_handle,&file));
CloseHandle(search_handle);
}
}
There really is no need to use 3rd party library to accomplish this. This is a short, independent function which lists all files (with their paths) in a directory, including subdiretories' files. std::string folderName has to finish with \, and if you want to list all files on computer, just create a loop in calling function along with GetLogicalDriveStrings (It returns strings with \, so it couldn't be more convenient in this case).
void FindAllFiles(std::string folderName)
{
WIN32_FIND_DATA FileData;
std::string folderNameWithSt = folderName + "*";
HANDLE FirstFile = FindFirstFile(folderNameWithSt.c_str(), &FileData);
if (FirstFile != INVALID_HANDLE_VALUE) {
do {
if (strcmp(FileData.cFileName, ".") != 0 && strcmp(FileData.cFileName, "..") != 0)
{
if(FileData.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY)
{
std::string NewPath = folderName + FileData.cFileName;
NewPath = NewPath + "\\";
FindAllFiles(NewPath);
}
else
{
std::cout /*<< folderName*/ << FileData.cFileName << std::endl;
}
}
} while(FindNextFile(FirstFile, &FileData));
}
}
This is ASCII version, remember that files and folders can be named in Unicode