Related
I'm working with an EFM32wg280f256 and I would like to debug the code that I'm writing in the following manner: opening a file in SD memory and write the content of the buffers I'm using.
This is a minimal example of my attempt:
#include <stdbool.h>
#include "ff.h"
#include <stdio.h>
#include <complex.h>
#include "arm_math.h"
#include "audioMoth.h"
#define NUMBER_OF_SAMPLES_IN_BUFFERS_DATA 4
static float32_t* buffersDATA[12];
int main(void) {
//Create buffers
buffersDATA[0] = (float32_t*)AM_EXTERNAL_SRAM_START_ADDRESS;
for (int i = 1; i < 12; i += 1) {
buffersDATA[i] = buffersDATA[i - 1] + NUMBER_OF_SAMPLES_IN_BUFFERS_DATA;
}
//Example of collected data
float32_t var0[] = {-29.499557,-67.498978,-54.499176,-53.499191};
//Pass collected data to one of created buffers
for (int j = 0; j <NUMBER_OF_SAMPLES_IN_BUFFERS_DATA; j+= 1){
*(buffersDATA[0]+j) = var0[j];
}
//Initialize file system
AudioMoth_enableFileSystem();
// Write text file
FIL fpt;
f_open(&fpt,"dataVAR.txt", FA_CREATE_ALWAYS | FA_WRITE);
for (int i = 0; i <NUMBER_OF_SAMPLES_IN_BUFFERS_DATA; i+= 1){
char str[8];
sprintf(str, "%d, ", (int)var0[i]);
f_puts(str,&fpt);
}
f_close(&fpt);
// Write another text file
FIL fptr;
f_open(&fptr,"data.txt", FA_CREATE_ALWAYS | FA_WRITE);
for (int i = 0; i <NUMBER_OF_SAMPLES_IN_BUFFERS_DATA; i+= 1){
char str[8];
sprintf(str, "%d, ", (int)*(buffersDATA[0]+i));
f_puts(str,&fptr);
}
f_close(&fptr);
}
Typecasting is because sprintf does not support float values, but integer is enough for me to know if I am doing OK or not.
When I open dataVAR.txt:
-29, -67, -54, -53,
But data.txt:
0, 0, 0, 0,
when they should be the same.
I've tried the same in a executable (adapting it) to verify that I am correctly passing the values (it seems so).
Where is the problem?
Thanks in advance.
Ok, the problem was that I didn't initialize communication between the microcontroller and the external chip of SRAM.
I did and all worked as expected.
How can I determine the list of files in a directory from inside my C or C++ code?
I'm not allowed to execute the ls command and parse the results from within my program.
UPDATE 2017:
In C++17 there is now an official way to list files of your file system: std::filesystem. There is an excellent answer from Shreevardhan below with this source code:
#include <string>
#include <iostream>
#include <filesystem>
namespace fs = std::filesystem;
int main()
{
std::string path = "/path/to/directory";
for (const auto & entry : fs::directory_iterator(path))
std::cout << entry.path() << std::endl;
}
Old Answer:
In small and simple tasks I do not use boost, I use dirent.h. It is available as a standard header in UNIX, and also available for Windows via a compatibility layer created by Toni Ronkko.
DIR *dir;
struct dirent *ent;
if ((dir = opendir ("c:\\src\\")) != NULL) {
/* print all the files and directories within directory */
while ((ent = readdir (dir)) != NULL) {
printf ("%s\n", ent->d_name);
}
closedir (dir);
} else {
/* could not open directory */
perror ("");
return EXIT_FAILURE;
}
It is just a small header file and does most of the simple stuff you need without using a big template-based approach like boost (no offence, I like boost!).
C++17 now has a std::filesystem::directory_iterator, which can be used as
#include <string>
#include <iostream>
#include <filesystem>
namespace fs = std::filesystem;
int main() {
std::string path = "/path/to/directory";
for (const auto & entry : fs::directory_iterator(path))
std::cout << entry.path() << std::endl;
}
Also, std::filesystem::recursive_directory_iterator can iterate the subdirectories as well.
Unfortunately the C++ standard does not define a standard way of working with files and folders in this way.
Since there is no cross platform way, the best cross platform way is to use a library such as the boost filesystem module.
Cross platform boost method:
The following function, given a directory path and a file name, recursively searches the directory and its sub-directories for the file name, returning a bool, and if successful, the path to the file that was found.
bool find_file(const path & dir_path, // in this directory,
const std::string & file_name, // search for this name,
path & path_found) // placing path here if found
{
if (!exists(dir_path))
return false;
directory_iterator end_itr; // default construction yields past-the-end
for (directory_iterator itr(dir_path); itr != end_itr; ++itr)
{
if (is_directory(itr->status()))
{
if (find_file(itr->path(), file_name, path_found))
return true;
}
else if (itr->leaf() == file_name) // see below
{
path_found = itr->path();
return true;
}
}
return false;
}
Source from the boost page mentioned above.
For Unix/Linux based systems:
You can use opendir / readdir / closedir.
Sample code which searches a directory for entry ``name'' is:
len = strlen(name);
dirp = opendir(".");
while ((dp = readdir(dirp)) != NULL)
if (dp->d_namlen == len && !strcmp(dp->d_name, name)) {
(void)closedir(dirp);
return FOUND;
}
(void)closedir(dirp);
return NOT_FOUND;
Source code from the above man pages.
For a windows based systems:
You can use the Win32 API FindFirstFile / FindNextFile / FindClose functions.
The following C++ example shows you a minimal use of FindFirstFile.
#include <windows.h>
#include <tchar.h>
#include <stdio.h>
void _tmain(int argc, TCHAR *argv[])
{
WIN32_FIND_DATA FindFileData;
HANDLE hFind;
if( argc != 2 )
{
_tprintf(TEXT("Usage: %s [target_file]\n"), argv[0]);
return;
}
_tprintf (TEXT("Target file is %s\n"), argv[1]);
hFind = FindFirstFile(argv[1], &FindFileData);
if (hFind == INVALID_HANDLE_VALUE)
{
printf ("FindFirstFile failed (%d)\n", GetLastError());
return;
}
else
{
_tprintf (TEXT("The first file found is %s\n"),
FindFileData.cFileName);
FindClose(hFind);
}
}
Source code from the above msdn pages.
One function is enough, you don't need to use any 3rd-party library (for Windows).
#include <Windows.h>
vector<string> get_all_files_names_within_folder(string folder)
{
vector<string> names;
string search_path = folder + "/*.*";
WIN32_FIND_DATA fd;
HANDLE hFind = ::FindFirstFile(search_path.c_str(), &fd);
if(hFind != INVALID_HANDLE_VALUE) {
do {
// read all (real) files in current folder
// , delete '!' read other 2 default folder . and ..
if(! (fd.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) ) {
names.push_back(fd.cFileName);
}
}while(::FindNextFile(hFind, &fd));
::FindClose(hFind);
}
return names;
}
PS: as mentioned by #Sebastian, you could change *.* to *.ext in order to get only the EXT-files (i.e. of a specific type) in that directory.
For a C only solution, please check this out. It only requires an extra header:
https://github.com/cxong/tinydir
tinydir_dir dir;
tinydir_open(&dir, "/path/to/dir");
while (dir.has_next)
{
tinydir_file file;
tinydir_readfile(&dir, &file);
printf("%s", file.name);
if (file.is_dir)
{
printf("/");
}
printf("\n");
tinydir_next(&dir);
}
tinydir_close(&dir);
Some advantages over other options:
It's portable - wraps POSIX dirent and Windows FindFirstFile
It uses readdir_r where available, which means it's (usually) threadsafe
Supports Windows UTF-16 via the same UNICODE macros
It is C90 so even very ancient compilers can use it
I recommend using glob with this reusable wrapper. It generates a vector<string> corresponding to file paths that fit the glob pattern:
#include <glob.h>
#include <vector>
using std::vector;
vector<string> globVector(const string& pattern){
glob_t glob_result;
glob(pattern.c_str(),GLOB_TILDE,NULL,&glob_result);
vector<string> files;
for(unsigned int i=0;i<glob_result.gl_pathc;++i){
files.push_back(string(glob_result.gl_pathv[i]));
}
globfree(&glob_result);
return files;
}
Which can then be called with a normal system wildcard pattern such as:
vector<string> files = globVector("./*");
I think, below snippet can be used to list all the files.
#include <stdio.h>
#include <dirent.h>
#include <sys/types.h>
int main(int argc, char** argv) {
list_dir("myFolderName");
return EXIT_SUCCESS;
}
static void list_dir(const char *path) {
struct dirent *entry;
DIR *dir = opendir(path);
if (dir == NULL) {
return;
}
while ((entry = readdir(dir)) != NULL) {
printf("%s\n",entry->d_name);
}
closedir(dir);
}
This is the structure used (present in dirent.h):
struct dirent {
ino_t d_ino; /* inode number */
off_t d_off; /* offset to the next dirent */
unsigned short d_reclen; /* length of this record */
unsigned char d_type; /* type of file */
char d_name[256]; /* filename */
};
Here is a very simple code in C++11 using boost::filesystem library to get file names in a directory (excluding folder names):
#include <string>
#include <iostream>
#include <boost/filesystem.hpp>
using namespace std;
using namespace boost::filesystem;
int main()
{
path p("D:/AnyFolder");
for (auto i = directory_iterator(p); i != directory_iterator(); i++)
{
if (!is_directory(i->path())) //we eliminate directories
{
cout << i->path().filename().string() << endl;
}
else
continue;
}
}
Output is like:
file1.txt
file2.dat
Why not use glob()?
#include <glob.h>
glob_t glob_result;
glob("/your_directory/*",GLOB_TILDE,NULL,&glob_result);
for(unsigned int i=0; i<glob_result.gl_pathc; ++i){
cout << glob_result.gl_pathv[i] << endl;
}
Try boost for x-platform method
http://www.boost.org/doc/libs/1_38_0/libs/filesystem/doc/index.htm
or just use your OS specific file stuff.
Check out this class which uses the win32 api. Just construct an instance by providing the foldername from which you want the listing then call the getNextFile method to get the next filename from the directory. I think it needs windows.h and stdio.h.
class FileGetter{
WIN32_FIND_DATAA found;
HANDLE hfind;
char folderstar[255];
int chk;
public:
FileGetter(char* folder){
sprintf(folderstar,"%s\\*.*",folder);
hfind = FindFirstFileA(folderstar,&found);
//skip .
FindNextFileA(hfind,&found);
}
int getNextFile(char* fname){
//skips .. when called for the first time
chk=FindNextFileA(hfind,&found);
if (chk)
strcpy(fname, found.cFileName);
return chk;
}
};
GNU Manual FTW
http://www.gnu.org/software/libc/manual/html_node/Simple-Directory-Lister.html#Simple-Directory-Lister
Also, sometimes it's good to go right to the source (pun intended). You can learn a lot by looking at the innards of some of the most common commands in Linux. I've set up a simple mirror of GNU's coreutils on github (for reading).
https://github.com/homer6/gnu_coreutils/blob/master/src/ls.c
Maybe this doesn't address Windows, but a number of cases of using Unix variants can be had by using these methods.
Hope that helps...
Shreevardhan answer works great. But if you want to use it in c++14 just make a change namespace fs = experimental::filesystem;
i.e.,
#include <string>
#include <iostream>
#include <filesystem>
using namespace std;
namespace fs = experimental::filesystem;
int main()
{
string path = "C:\\splits\\";
for (auto & p : fs::directory_iterator(path))
cout << p << endl;
int n;
cin >> n;
}
#include <string>
#include <iostream>
#include <filesystem>
namespace fs = std::filesystem;
int main() {
std::string path = "/path/to/directory";
for (const auto & entry : fs::directory_iterator(path))
std::cout << entry.path() << std::endl;
}
I hope this code help you.
#include <windows.h>
#include <iostream>
#include <string>
#include <vector>
using namespace std;
string wchar_t2string(const wchar_t *wchar)
{
string str = "";
int index = 0;
while(wchar[index] != 0)
{
str += (char)wchar[index];
++index;
}
return str;
}
wchar_t *string2wchar_t(const string &str)
{
wchar_t wchar[260];
int index = 0;
while(index < str.size())
{
wchar[index] = (wchar_t)str[index];
++index;
}
wchar[index] = 0;
return wchar;
}
vector<string> listFilesInDirectory(string directoryName)
{
WIN32_FIND_DATA FindFileData;
wchar_t * FileName = string2wchar_t(directoryName);
HANDLE hFind = FindFirstFile(FileName, &FindFileData);
vector<string> listFileNames;
listFileNames.push_back(wchar_t2string(FindFileData.cFileName));
while (FindNextFile(hFind, &FindFileData))
listFileNames.push_back(wchar_t2string(FindFileData.cFileName));
return listFileNames;
}
void main()
{
vector<string> listFiles;
listFiles = listFilesInDirectory("C:\\*.txt");
for each (string str in listFiles)
cout << str << endl;
}
char **getKeys(char *data_dir, char* tablename, int *num_keys)
{
char** arr = malloc(MAX_RECORDS_PER_TABLE*sizeof(char*));
int i = 0;
for (;i < MAX_RECORDS_PER_TABLE; i++)
arr[i] = malloc( (MAX_KEY_LEN+1) * sizeof(char) );
char *buf = (char *)malloc( (MAX_KEY_LEN+1)*sizeof(char) );
snprintf(buf, MAX_KEY_LEN+1, "%s/%s", data_dir, tablename);
DIR* tableDir = opendir(buf);
struct dirent* getInfo;
readdir(tableDir); // ignore '.'
readdir(tableDir); // ignore '..'
i = 0;
while(1)
{
getInfo = readdir(tableDir);
if (getInfo == 0)
break;
strcpy(arr[i++], getInfo->d_name);
}
*(num_keys) = i;
return arr;
}
This implementation realizes your purpose, dynamically filling an array of strings with the content of the specified directory.
int exploreDirectory(const char *dirpath, char ***list, int *numItems) {
struct dirent **direntList;
int i;
errno = 0;
if ((*numItems = scandir(dirpath, &direntList, NULL, alphasort)) == -1)
return errno;
if (!((*list) = malloc(sizeof(char *) * (*numItems)))) {
fprintf(stderr, "Error in list allocation for file list: dirpath=%s.\n", dirpath);
exit(EXIT_FAILURE);
}
for (i = 0; i < *numItems; i++) {
(*list)[i] = stringDuplication(direntList[i]->d_name);
}
for (i = 0; i < *numItems; i++) {
free(direntList[i]);
}
free(direntList);
return 0;
}
This works for me. I'm sorry if I cannot remember the source. It is probably from a man page.
#include <ftw.h>
int AnalizeDirectoryElement (const char *fpath,
const struct stat *sb,
int tflag,
struct FTW *ftwbuf) {
if (tflag == FTW_F) {
std::string strFileName(fpath);
DoSomethingWith(strFileName);
}
return 0;
}
void WalkDirectoryTree (const char * pchFileName) {
int nFlags = 0;
if (nftw(pchFileName, AnalizeDirectoryElement, 20, nFlags) == -1) {
perror("nftw");
}
}
int main() {
WalkDirectoryTree("some_dir/");
}
you can get all direct of files in your root directory by using std::experimental:: filesystem::directory_iterator(). Then, read the name of these pathfiles.
#include <iostream>
#include <filesystem>
#include <string>
#include <direct.h>
using namespace std;
namespace fs = std::experimental::filesystem;
void ShowListFile(string path)
{
for(auto &p: fs::directory_iterator(path)) /*get directory */
cout<<p.path().filename()<<endl; // get file name
}
int main() {
ShowListFile("C:/Users/dell/Pictures/Camera Roll/");
getchar();
return 0;
}
This answer should work for Windows users that have had trouble getting this working with Visual Studio with any of the other answers.
Download the dirent.h file from the github page. But is better to just use the Raw dirent.h file and follow my steps below (it is how I got it to work).
Github page for dirent.h for Windows: Github page for dirent.h
Raw Dirent File: Raw dirent.h File
Go to your project and Add a new Item (Ctrl+Shift+A). Add a header file (.h) and name it dirent.h.
Paste the Raw dirent.h File code into your header.
Include "dirent.h" in your code.
Put the below void filefinder() method in your code and call it from your main function or edit the function how you want to use it.
#include <stdio.h>
#include <string.h>
#include "dirent.h"
string path = "C:/folder"; //Put a valid path here for folder
void filefinder()
{
DIR *directory = opendir(path.c_str());
struct dirent *direntStruct;
if (directory != NULL) {
while (direntStruct = readdir(directory)) {
printf("File Name: %s\n", direntStruct->d_name); //If you are using <stdio.h>
//std::cout << direntStruct->d_name << std::endl; //If you are using <iostream>
}
}
closedir(directory);
}
I tried to follow the example given in both answers and it might be worth noting that it appears as though std::filesystem::directory_entry has been changed to not have an overload of the << operator. Instead of std::cout << p << std::endl; I had to use the following to be able to compile and get it working:
#include <iostream>
#include <filesystem>
#include <string>
namespace fs = std::filesystem;
int main() {
std::string path = "/path/to/directory";
for(const auto& p : fs::directory_iterator(path))
std::cout << p.path() << std::endl;
}
trying to pass p on its own to std::cout << resulted in a missing overload error.
Peter Parker's solution, but without using for:
#include <algorithm>
#include <filesystem>
#include <ranges>
#include <vector>
using namespace std;
int main() {
vector<filesystem::path> filePaths;
ranges::transform(filesystem::directory_iterator("."),
back_inserter(filePaths), [](const auto& dirFile){return dirFile.path();} );
}
System call it!
system( "dir /b /s /a-d * > file_names.txt" );
Then just read the file.
EDIT: This answer should be considered a hack, but it really does work (albeit in a platform specific way) if you don't have access to more elegant solutions.
Since files and sub directories of a directory are generally stored in a tree structure, an intuitive way is to use DFS algorithm to recursively traverse each of them.
Here is an example in windows operating system by using basic file functions in io.h. You can replace these functions in other platform. What I want to express is that the basic idea of DFS perfectly meets this problem.
#include<io.h>
#include<iostream.h>
#include<string>
using namespace std;
void TraverseFilesUsingDFS(const string& folder_path){
_finddata_t file_info;
string any_file_pattern = folder_path + "\\*";
intptr_t handle = _findfirst(any_file_pattern.c_str(),&file_info);
//If folder_path exsist, using any_file_pattern will find at least two files "." and "..",
//of which "." means current dir and ".." means parent dir
if (handle == -1){
cerr << "folder path not exist: " << folder_path << endl;
exit(-1);
}
//iteratively check each file or sub_directory in current folder
do{
string file_name=file_info.name; //from char array to string
//check whtether it is a sub direcotry or a file
if (file_info.attrib & _A_SUBDIR){
if (file_name != "." && file_name != ".."){
string sub_folder_path = folder_path + "\\" + file_name;
TraverseFilesUsingDFS(sub_folder_path);
cout << "a sub_folder path: " << sub_folder_path << endl;
}
}
else
cout << "file name: " << file_name << endl;
} while (_findnext(handle, &file_info) == 0);
//
_findclose(handle);
}
Building on what herohuyongtao posted and a few other posts:
http://www.cplusplus.com/forum/general/39766/
What is the expected input type of FindFirstFile?
How to convert wstring into string?
This is a Windows solution.
Since I wanted to pass in std::string and return a vector of strings I had to make a couple conversions.
#include <string>
#include <Windows.h>
#include <vector>
#include <locale>
#include <codecvt>
std::vector<std::string> listFilesInDir(std::string path)
{
std::vector<std::string> names;
//Convert string to wstring
std::wstring search_path = std::wstring_convert<std::codecvt_utf8<wchar_t>>().from_bytes(path);
WIN32_FIND_DATA fd;
HANDLE hFind = FindFirstFile(search_path.c_str(), &fd);
if (hFind != INVALID_HANDLE_VALUE)
{
do
{
// read all (real) files in current folder
// , delete '!' read other 2 default folder . and ..
if (!(fd.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY))
{
//convert from wide char to narrow char array
char ch[260];
char DefChar = ' ';
WideCharToMultiByte(CP_ACP, 0, fd.cFileName, -1, ch, 260, &DefChar, NULL);
names.push_back(ch);
}
}
while (::FindNextFile(hFind, &fd));
::FindClose(hFind);
}
return names;
}
Based on the answers above
#include <vector>
#include <string>
#include <algorithm>
#ifdef _WIN32
#include <windows.h>
std::vector<std::string> files_in_directory(std::string path)
{
std::vector<std::string> files;
// check directory exists
char fullpath[MAX_PATH];
GetFullPathName(path.c_str(), MAX_PATH, fullpath, 0);
std::string fp(fullpath);
if (GetFileAttributes(fp.c_str()) != FILE_ATTRIBUTE_DIRECTORY)
return files;
// get file names
WIN32_FIND_DATA findfiledata;
HANDLE hFind = FindFirstFile((LPCSTR)(fp + "\\*").c_str(), &findfiledata);
if (hFind != INVALID_HANDLE_VALUE)
{
do
{
files.push_back(findfiledata.cFileName);
}
while (FindNextFile(hFind, &findfiledata));
FindClose(hFind);
}
// delete current and parent directories
files.erase(std::find(files.begin(), files.end(), "."));
files.erase(std::find(files.begin(), files.end(), ".."));
// sort in alphabetical order
std::sort(files.begin(), files.end());
return files;
}
#else
#include <dirent.h>
std::vector<std::string> files_in_directory(std::string directory)
{
std::vector<std::string> files;
// open directory
DIR *dir;
dir = opendir(directory.c_str());
if (dir == NULL)
return files;
// get file names
struct dirent *ent;
while ((ent = readdir(dir)) != NULL)
files.push_back(ent->d_name);
closedir(dir);
// delete current and parent directories
files.erase(std::find(files.begin(), files.end(), "."));
files.erase(std::find(files.begin(), files.end(), ".."));
// sort in alphabetical order
std::sort(files.begin(), files.end());
return files;
}
#endif // _WIN32
Shreevardhan's design also works great for traversing subdirectories:
#include <string>
#include <iostream>
#include <filesystem>
using namespace std;
namespace fs = filesystem;
int main()
{
string path = "\\path\\to\\directory";
// string path = "/path/to/directory";
for (auto & p : fs::recursive_directory_iterator(path))
cout << p.path() << endl;
}
Compilation: cl /EHsc /W4 /WX /std:c++17 ListFiles.cpp
Simply in Linux use following ASCI C style code
#include <bits/stdc++.h>
#include <dirent.h>
using namespace std;
int main(){
DIR *dpdf;
struct dirent *epdf;
dpdf = opendir("./");
if (dpdf != NULL){
while (epdf = readdir(dpdf)){
cout << epdf->d_name << std::endl;
}
}
closedir(dpdf);
return 0;
}
Hope this helps!
Just something that I want to share and thank you for the reading material. Play around with the function for a bit to understand it. You may like it. e stood for extension, p is for path, and s is for path separator.
If the path is passed without ending separator, a separator will be appended to the path. For the extension, if an empty string is inputted then the function will return any file that does not have an extension in its name. If a single star was inputted than all files in the directory will be returned. If e length is greater than 0 but is not a single * then a dot will be prepended to e if e had not contained a dot at the zero position.
For a returning value. If a zero-length map is returned then nothing was found but the directory was open okay. If index 999 is available from the return value but the map size is only 1 then that meant there was a problem with opening the directory path.
Note that for efficiency, this function can be split into 3 smaller functions. On top of that, you can create a caller function that will detect which function it is going to call based on the input. Why is that more efficient? Said if you are going to grab everything that is a file, doing that method the subfunction that built for grabbing all the files will just grab all that are files and does not need to evaluate any other unnecessary condition everytime it found a file.
That would also apply to when you grab files that do not have an extension. A specific built function for that purpose would only evaluate for weather if the object found is a file and then whether or not if the name of the file has a dot in it.
The saving may not be much if you only read directories with not so much files. But if you are reading a mass amount of directory or if the directory has couple hundred thousands of files, it could be a huge saving.
#include <stdio.h>
#include <sys/stat.h>
#include <iostream>
#include <dirent.h>
#include <map>
std::map<int, std::string> getFile(std::string p, std::string e = "", unsigned char s = '/'){
if ( p.size() > 0 ){
if (p.back() != s) p += s;
}
if ( e.size() > 0 ){
if ( e.at(0) != '.' && !(e.size() == 1 && e.at(0) == '*') ) e = "." + e;
}
DIR *dir;
struct dirent *ent;
struct stat sb;
std::map<int, std::string> r = {{999, "FAILED"}};
std::string temp;
int f = 0;
bool fd;
if ( (dir = opendir(p.c_str())) != NULL ){
r.erase (999);
while ((ent = readdir (dir)) != NULL){
temp = ent->d_name;
fd = temp.find(".") != std::string::npos? true : false;
temp = p + temp;
if (stat(temp.c_str(), &sb) == 0 && S_ISREG(sb.st_mode)){
if ( e.size() == 1 && e.at(0) == '*' ){
r[f] = temp;
f++;
} else {
if (e.size() == 0){
if ( fd == false ){
r[f] = temp;
f++;
}
continue;
}
if (e.size() > temp.size()) continue;
if ( temp.substr(temp.size() - e.size()) == e ){
r[f] = temp;
f++;
}
}
}
}
closedir(dir);
return r;
} else {
return r;
}
}
void printMap(auto &m){
for (const auto &p : m) {
std::cout << "m[" << p.first << "] = " << p.second << std::endl;
}
}
int main(){
std::map<int, std::string> k = getFile("./", "");
printMap(k);
return 0;
}
#include<iostream>
#include <dirent.h>
using namespace std;
char ROOT[]={'.'};
void listfiles(char* path){
DIR * dirp = opendir(path);
dirent * dp;
while ( (dp = readdir(dirp)) !=NULL ) {
cout << dp->d_name << " size " << dp->d_reclen<<std::endl;
}
(void)closedir(dirp);
}
int main(int argc, char **argv)
{
char* path;
if (argc>1) path=argv[1]; else path=ROOT;
cout<<"list files in ["<<path<<"]"<<std::endl;
listfiles(path);
return 0;
}
How can I determine the list of files in a directory from inside my C or C++ code?
I'm not allowed to execute the ls command and parse the results from within my program.
UPDATE 2017:
In C++17 there is now an official way to list files of your file system: std::filesystem. There is an excellent answer from Shreevardhan below with this source code:
#include <string>
#include <iostream>
#include <filesystem>
namespace fs = std::filesystem;
int main()
{
std::string path = "/path/to/directory";
for (const auto & entry : fs::directory_iterator(path))
std::cout << entry.path() << std::endl;
}
Old Answer:
In small and simple tasks I do not use boost, I use dirent.h. It is available as a standard header in UNIX, and also available for Windows via a compatibility layer created by Toni Ronkko.
DIR *dir;
struct dirent *ent;
if ((dir = opendir ("c:\\src\\")) != NULL) {
/* print all the files and directories within directory */
while ((ent = readdir (dir)) != NULL) {
printf ("%s\n", ent->d_name);
}
closedir (dir);
} else {
/* could not open directory */
perror ("");
return EXIT_FAILURE;
}
It is just a small header file and does most of the simple stuff you need without using a big template-based approach like boost (no offence, I like boost!).
C++17 now has a std::filesystem::directory_iterator, which can be used as
#include <string>
#include <iostream>
#include <filesystem>
namespace fs = std::filesystem;
int main() {
std::string path = "/path/to/directory";
for (const auto & entry : fs::directory_iterator(path))
std::cout << entry.path() << std::endl;
}
Also, std::filesystem::recursive_directory_iterator can iterate the subdirectories as well.
Unfortunately the C++ standard does not define a standard way of working with files and folders in this way.
Since there is no cross platform way, the best cross platform way is to use a library such as the boost filesystem module.
Cross platform boost method:
The following function, given a directory path and a file name, recursively searches the directory and its sub-directories for the file name, returning a bool, and if successful, the path to the file that was found.
bool find_file(const path & dir_path, // in this directory,
const std::string & file_name, // search for this name,
path & path_found) // placing path here if found
{
if (!exists(dir_path))
return false;
directory_iterator end_itr; // default construction yields past-the-end
for (directory_iterator itr(dir_path); itr != end_itr; ++itr)
{
if (is_directory(itr->status()))
{
if (find_file(itr->path(), file_name, path_found))
return true;
}
else if (itr->leaf() == file_name) // see below
{
path_found = itr->path();
return true;
}
}
return false;
}
Source from the boost page mentioned above.
For Unix/Linux based systems:
You can use opendir / readdir / closedir.
Sample code which searches a directory for entry ``name'' is:
len = strlen(name);
dirp = opendir(".");
while ((dp = readdir(dirp)) != NULL)
if (dp->d_namlen == len && !strcmp(dp->d_name, name)) {
(void)closedir(dirp);
return FOUND;
}
(void)closedir(dirp);
return NOT_FOUND;
Source code from the above man pages.
For a windows based systems:
You can use the Win32 API FindFirstFile / FindNextFile / FindClose functions.
The following C++ example shows you a minimal use of FindFirstFile.
#include <windows.h>
#include <tchar.h>
#include <stdio.h>
void _tmain(int argc, TCHAR *argv[])
{
WIN32_FIND_DATA FindFileData;
HANDLE hFind;
if( argc != 2 )
{
_tprintf(TEXT("Usage: %s [target_file]\n"), argv[0]);
return;
}
_tprintf (TEXT("Target file is %s\n"), argv[1]);
hFind = FindFirstFile(argv[1], &FindFileData);
if (hFind == INVALID_HANDLE_VALUE)
{
printf ("FindFirstFile failed (%d)\n", GetLastError());
return;
}
else
{
_tprintf (TEXT("The first file found is %s\n"),
FindFileData.cFileName);
FindClose(hFind);
}
}
Source code from the above msdn pages.
One function is enough, you don't need to use any 3rd-party library (for Windows).
#include <Windows.h>
vector<string> get_all_files_names_within_folder(string folder)
{
vector<string> names;
string search_path = folder + "/*.*";
WIN32_FIND_DATA fd;
HANDLE hFind = ::FindFirstFile(search_path.c_str(), &fd);
if(hFind != INVALID_HANDLE_VALUE) {
do {
// read all (real) files in current folder
// , delete '!' read other 2 default folder . and ..
if(! (fd.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) ) {
names.push_back(fd.cFileName);
}
}while(::FindNextFile(hFind, &fd));
::FindClose(hFind);
}
return names;
}
PS: as mentioned by #Sebastian, you could change *.* to *.ext in order to get only the EXT-files (i.e. of a specific type) in that directory.
For a C only solution, please check this out. It only requires an extra header:
https://github.com/cxong/tinydir
tinydir_dir dir;
tinydir_open(&dir, "/path/to/dir");
while (dir.has_next)
{
tinydir_file file;
tinydir_readfile(&dir, &file);
printf("%s", file.name);
if (file.is_dir)
{
printf("/");
}
printf("\n");
tinydir_next(&dir);
}
tinydir_close(&dir);
Some advantages over other options:
It's portable - wraps POSIX dirent and Windows FindFirstFile
It uses readdir_r where available, which means it's (usually) threadsafe
Supports Windows UTF-16 via the same UNICODE macros
It is C90 so even very ancient compilers can use it
I recommend using glob with this reusable wrapper. It generates a vector<string> corresponding to file paths that fit the glob pattern:
#include <glob.h>
#include <vector>
using std::vector;
vector<string> globVector(const string& pattern){
glob_t glob_result;
glob(pattern.c_str(),GLOB_TILDE,NULL,&glob_result);
vector<string> files;
for(unsigned int i=0;i<glob_result.gl_pathc;++i){
files.push_back(string(glob_result.gl_pathv[i]));
}
globfree(&glob_result);
return files;
}
Which can then be called with a normal system wildcard pattern such as:
vector<string> files = globVector("./*");
I think, below snippet can be used to list all the files.
#include <stdio.h>
#include <dirent.h>
#include <sys/types.h>
int main(int argc, char** argv) {
list_dir("myFolderName");
return EXIT_SUCCESS;
}
static void list_dir(const char *path) {
struct dirent *entry;
DIR *dir = opendir(path);
if (dir == NULL) {
return;
}
while ((entry = readdir(dir)) != NULL) {
printf("%s\n",entry->d_name);
}
closedir(dir);
}
This is the structure used (present in dirent.h):
struct dirent {
ino_t d_ino; /* inode number */
off_t d_off; /* offset to the next dirent */
unsigned short d_reclen; /* length of this record */
unsigned char d_type; /* type of file */
char d_name[256]; /* filename */
};
Here is a very simple code in C++11 using boost::filesystem library to get file names in a directory (excluding folder names):
#include <string>
#include <iostream>
#include <boost/filesystem.hpp>
using namespace std;
using namespace boost::filesystem;
int main()
{
path p("D:/AnyFolder");
for (auto i = directory_iterator(p); i != directory_iterator(); i++)
{
if (!is_directory(i->path())) //we eliminate directories
{
cout << i->path().filename().string() << endl;
}
else
continue;
}
}
Output is like:
file1.txt
file2.dat
Why not use glob()?
#include <glob.h>
glob_t glob_result;
glob("/your_directory/*",GLOB_TILDE,NULL,&glob_result);
for(unsigned int i=0; i<glob_result.gl_pathc; ++i){
cout << glob_result.gl_pathv[i] << endl;
}
Try boost for x-platform method
http://www.boost.org/doc/libs/1_38_0/libs/filesystem/doc/index.htm
or just use your OS specific file stuff.
Check out this class which uses the win32 api. Just construct an instance by providing the foldername from which you want the listing then call the getNextFile method to get the next filename from the directory. I think it needs windows.h and stdio.h.
class FileGetter{
WIN32_FIND_DATAA found;
HANDLE hfind;
char folderstar[255];
int chk;
public:
FileGetter(char* folder){
sprintf(folderstar,"%s\\*.*",folder);
hfind = FindFirstFileA(folderstar,&found);
//skip .
FindNextFileA(hfind,&found);
}
int getNextFile(char* fname){
//skips .. when called for the first time
chk=FindNextFileA(hfind,&found);
if (chk)
strcpy(fname, found.cFileName);
return chk;
}
};
GNU Manual FTW
http://www.gnu.org/software/libc/manual/html_node/Simple-Directory-Lister.html#Simple-Directory-Lister
Also, sometimes it's good to go right to the source (pun intended). You can learn a lot by looking at the innards of some of the most common commands in Linux. I've set up a simple mirror of GNU's coreutils on github (for reading).
https://github.com/homer6/gnu_coreutils/blob/master/src/ls.c
Maybe this doesn't address Windows, but a number of cases of using Unix variants can be had by using these methods.
Hope that helps...
Shreevardhan answer works great. But if you want to use it in c++14 just make a change namespace fs = experimental::filesystem;
i.e.,
#include <string>
#include <iostream>
#include <filesystem>
using namespace std;
namespace fs = experimental::filesystem;
int main()
{
string path = "C:\\splits\\";
for (auto & p : fs::directory_iterator(path))
cout << p << endl;
int n;
cin >> n;
}
#include <string>
#include <iostream>
#include <filesystem>
namespace fs = std::filesystem;
int main() {
std::string path = "/path/to/directory";
for (const auto & entry : fs::directory_iterator(path))
std::cout << entry.path() << std::endl;
}
I hope this code help you.
#include <windows.h>
#include <iostream>
#include <string>
#include <vector>
using namespace std;
string wchar_t2string(const wchar_t *wchar)
{
string str = "";
int index = 0;
while(wchar[index] != 0)
{
str += (char)wchar[index];
++index;
}
return str;
}
wchar_t *string2wchar_t(const string &str)
{
wchar_t wchar[260];
int index = 0;
while(index < str.size())
{
wchar[index] = (wchar_t)str[index];
++index;
}
wchar[index] = 0;
return wchar;
}
vector<string> listFilesInDirectory(string directoryName)
{
WIN32_FIND_DATA FindFileData;
wchar_t * FileName = string2wchar_t(directoryName);
HANDLE hFind = FindFirstFile(FileName, &FindFileData);
vector<string> listFileNames;
listFileNames.push_back(wchar_t2string(FindFileData.cFileName));
while (FindNextFile(hFind, &FindFileData))
listFileNames.push_back(wchar_t2string(FindFileData.cFileName));
return listFileNames;
}
void main()
{
vector<string> listFiles;
listFiles = listFilesInDirectory("C:\\*.txt");
for each (string str in listFiles)
cout << str << endl;
}
char **getKeys(char *data_dir, char* tablename, int *num_keys)
{
char** arr = malloc(MAX_RECORDS_PER_TABLE*sizeof(char*));
int i = 0;
for (;i < MAX_RECORDS_PER_TABLE; i++)
arr[i] = malloc( (MAX_KEY_LEN+1) * sizeof(char) );
char *buf = (char *)malloc( (MAX_KEY_LEN+1)*sizeof(char) );
snprintf(buf, MAX_KEY_LEN+1, "%s/%s", data_dir, tablename);
DIR* tableDir = opendir(buf);
struct dirent* getInfo;
readdir(tableDir); // ignore '.'
readdir(tableDir); // ignore '..'
i = 0;
while(1)
{
getInfo = readdir(tableDir);
if (getInfo == 0)
break;
strcpy(arr[i++], getInfo->d_name);
}
*(num_keys) = i;
return arr;
}
This implementation realizes your purpose, dynamically filling an array of strings with the content of the specified directory.
int exploreDirectory(const char *dirpath, char ***list, int *numItems) {
struct dirent **direntList;
int i;
errno = 0;
if ((*numItems = scandir(dirpath, &direntList, NULL, alphasort)) == -1)
return errno;
if (!((*list) = malloc(sizeof(char *) * (*numItems)))) {
fprintf(stderr, "Error in list allocation for file list: dirpath=%s.\n", dirpath);
exit(EXIT_FAILURE);
}
for (i = 0; i < *numItems; i++) {
(*list)[i] = stringDuplication(direntList[i]->d_name);
}
for (i = 0; i < *numItems; i++) {
free(direntList[i]);
}
free(direntList);
return 0;
}
This works for me. I'm sorry if I cannot remember the source. It is probably from a man page.
#include <ftw.h>
int AnalizeDirectoryElement (const char *fpath,
const struct stat *sb,
int tflag,
struct FTW *ftwbuf) {
if (tflag == FTW_F) {
std::string strFileName(fpath);
DoSomethingWith(strFileName);
}
return 0;
}
void WalkDirectoryTree (const char * pchFileName) {
int nFlags = 0;
if (nftw(pchFileName, AnalizeDirectoryElement, 20, nFlags) == -1) {
perror("nftw");
}
}
int main() {
WalkDirectoryTree("some_dir/");
}
you can get all direct of files in your root directory by using std::experimental:: filesystem::directory_iterator(). Then, read the name of these pathfiles.
#include <iostream>
#include <filesystem>
#include <string>
#include <direct.h>
using namespace std;
namespace fs = std::experimental::filesystem;
void ShowListFile(string path)
{
for(auto &p: fs::directory_iterator(path)) /*get directory */
cout<<p.path().filename()<<endl; // get file name
}
int main() {
ShowListFile("C:/Users/dell/Pictures/Camera Roll/");
getchar();
return 0;
}
This answer should work for Windows users that have had trouble getting this working with Visual Studio with any of the other answers.
Download the dirent.h file from the github page. But is better to just use the Raw dirent.h file and follow my steps below (it is how I got it to work).
Github page for dirent.h for Windows: Github page for dirent.h
Raw Dirent File: Raw dirent.h File
Go to your project and Add a new Item (Ctrl+Shift+A). Add a header file (.h) and name it dirent.h.
Paste the Raw dirent.h File code into your header.
Include "dirent.h" in your code.
Put the below void filefinder() method in your code and call it from your main function or edit the function how you want to use it.
#include <stdio.h>
#include <string.h>
#include "dirent.h"
string path = "C:/folder"; //Put a valid path here for folder
void filefinder()
{
DIR *directory = opendir(path.c_str());
struct dirent *direntStruct;
if (directory != NULL) {
while (direntStruct = readdir(directory)) {
printf("File Name: %s\n", direntStruct->d_name); //If you are using <stdio.h>
//std::cout << direntStruct->d_name << std::endl; //If you are using <iostream>
}
}
closedir(directory);
}
I tried to follow the example given in both answers and it might be worth noting that it appears as though std::filesystem::directory_entry has been changed to not have an overload of the << operator. Instead of std::cout << p << std::endl; I had to use the following to be able to compile and get it working:
#include <iostream>
#include <filesystem>
#include <string>
namespace fs = std::filesystem;
int main() {
std::string path = "/path/to/directory";
for(const auto& p : fs::directory_iterator(path))
std::cout << p.path() << std::endl;
}
trying to pass p on its own to std::cout << resulted in a missing overload error.
Peter Parker's solution, but without using for:
#include <algorithm>
#include <filesystem>
#include <ranges>
#include <vector>
using namespace std;
int main() {
vector<filesystem::path> filePaths;
ranges::transform(filesystem::directory_iterator("."),
back_inserter(filePaths), [](const auto& dirFile){return dirFile.path();} );
}
System call it!
system( "dir /b /s /a-d * > file_names.txt" );
Then just read the file.
EDIT: This answer should be considered a hack, but it really does work (albeit in a platform specific way) if you don't have access to more elegant solutions.
Since files and sub directories of a directory are generally stored in a tree structure, an intuitive way is to use DFS algorithm to recursively traverse each of them.
Here is an example in windows operating system by using basic file functions in io.h. You can replace these functions in other platform. What I want to express is that the basic idea of DFS perfectly meets this problem.
#include<io.h>
#include<iostream.h>
#include<string>
using namespace std;
void TraverseFilesUsingDFS(const string& folder_path){
_finddata_t file_info;
string any_file_pattern = folder_path + "\\*";
intptr_t handle = _findfirst(any_file_pattern.c_str(),&file_info);
//If folder_path exsist, using any_file_pattern will find at least two files "." and "..",
//of which "." means current dir and ".." means parent dir
if (handle == -1){
cerr << "folder path not exist: " << folder_path << endl;
exit(-1);
}
//iteratively check each file or sub_directory in current folder
do{
string file_name=file_info.name; //from char array to string
//check whtether it is a sub direcotry or a file
if (file_info.attrib & _A_SUBDIR){
if (file_name != "." && file_name != ".."){
string sub_folder_path = folder_path + "\\" + file_name;
TraverseFilesUsingDFS(sub_folder_path);
cout << "a sub_folder path: " << sub_folder_path << endl;
}
}
else
cout << "file name: " << file_name << endl;
} while (_findnext(handle, &file_info) == 0);
//
_findclose(handle);
}
Building on what herohuyongtao posted and a few other posts:
http://www.cplusplus.com/forum/general/39766/
What is the expected input type of FindFirstFile?
How to convert wstring into string?
This is a Windows solution.
Since I wanted to pass in std::string and return a vector of strings I had to make a couple conversions.
#include <string>
#include <Windows.h>
#include <vector>
#include <locale>
#include <codecvt>
std::vector<std::string> listFilesInDir(std::string path)
{
std::vector<std::string> names;
//Convert string to wstring
std::wstring search_path = std::wstring_convert<std::codecvt_utf8<wchar_t>>().from_bytes(path);
WIN32_FIND_DATA fd;
HANDLE hFind = FindFirstFile(search_path.c_str(), &fd);
if (hFind != INVALID_HANDLE_VALUE)
{
do
{
// read all (real) files in current folder
// , delete '!' read other 2 default folder . and ..
if (!(fd.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY))
{
//convert from wide char to narrow char array
char ch[260];
char DefChar = ' ';
WideCharToMultiByte(CP_ACP, 0, fd.cFileName, -1, ch, 260, &DefChar, NULL);
names.push_back(ch);
}
}
while (::FindNextFile(hFind, &fd));
::FindClose(hFind);
}
return names;
}
Based on the answers above
#include <vector>
#include <string>
#include <algorithm>
#ifdef _WIN32
#include <windows.h>
std::vector<std::string> files_in_directory(std::string path)
{
std::vector<std::string> files;
// check directory exists
char fullpath[MAX_PATH];
GetFullPathName(path.c_str(), MAX_PATH, fullpath, 0);
std::string fp(fullpath);
if (GetFileAttributes(fp.c_str()) != FILE_ATTRIBUTE_DIRECTORY)
return files;
// get file names
WIN32_FIND_DATA findfiledata;
HANDLE hFind = FindFirstFile((LPCSTR)(fp + "\\*").c_str(), &findfiledata);
if (hFind != INVALID_HANDLE_VALUE)
{
do
{
files.push_back(findfiledata.cFileName);
}
while (FindNextFile(hFind, &findfiledata));
FindClose(hFind);
}
// delete current and parent directories
files.erase(std::find(files.begin(), files.end(), "."));
files.erase(std::find(files.begin(), files.end(), ".."));
// sort in alphabetical order
std::sort(files.begin(), files.end());
return files;
}
#else
#include <dirent.h>
std::vector<std::string> files_in_directory(std::string directory)
{
std::vector<std::string> files;
// open directory
DIR *dir;
dir = opendir(directory.c_str());
if (dir == NULL)
return files;
// get file names
struct dirent *ent;
while ((ent = readdir(dir)) != NULL)
files.push_back(ent->d_name);
closedir(dir);
// delete current and parent directories
files.erase(std::find(files.begin(), files.end(), "."));
files.erase(std::find(files.begin(), files.end(), ".."));
// sort in alphabetical order
std::sort(files.begin(), files.end());
return files;
}
#endif // _WIN32
Shreevardhan's design also works great for traversing subdirectories:
#include <string>
#include <iostream>
#include <filesystem>
using namespace std;
namespace fs = filesystem;
int main()
{
string path = "\\path\\to\\directory";
// string path = "/path/to/directory";
for (auto & p : fs::recursive_directory_iterator(path))
cout << p.path() << endl;
}
Compilation: cl /EHsc /W4 /WX /std:c++17 ListFiles.cpp
Simply in Linux use following ASCI C style code
#include <bits/stdc++.h>
#include <dirent.h>
using namespace std;
int main(){
DIR *dpdf;
struct dirent *epdf;
dpdf = opendir("./");
if (dpdf != NULL){
while (epdf = readdir(dpdf)){
cout << epdf->d_name << std::endl;
}
}
closedir(dpdf);
return 0;
}
Hope this helps!
Just something that I want to share and thank you for the reading material. Play around with the function for a bit to understand it. You may like it. e stood for extension, p is for path, and s is for path separator.
If the path is passed without ending separator, a separator will be appended to the path. For the extension, if an empty string is inputted then the function will return any file that does not have an extension in its name. If a single star was inputted than all files in the directory will be returned. If e length is greater than 0 but is not a single * then a dot will be prepended to e if e had not contained a dot at the zero position.
For a returning value. If a zero-length map is returned then nothing was found but the directory was open okay. If index 999 is available from the return value but the map size is only 1 then that meant there was a problem with opening the directory path.
Note that for efficiency, this function can be split into 3 smaller functions. On top of that, you can create a caller function that will detect which function it is going to call based on the input. Why is that more efficient? Said if you are going to grab everything that is a file, doing that method the subfunction that built for grabbing all the files will just grab all that are files and does not need to evaluate any other unnecessary condition everytime it found a file.
That would also apply to when you grab files that do not have an extension. A specific built function for that purpose would only evaluate for weather if the object found is a file and then whether or not if the name of the file has a dot in it.
The saving may not be much if you only read directories with not so much files. But if you are reading a mass amount of directory or if the directory has couple hundred thousands of files, it could be a huge saving.
#include <stdio.h>
#include <sys/stat.h>
#include <iostream>
#include <dirent.h>
#include <map>
std::map<int, std::string> getFile(std::string p, std::string e = "", unsigned char s = '/'){
if ( p.size() > 0 ){
if (p.back() != s) p += s;
}
if ( e.size() > 0 ){
if ( e.at(0) != '.' && !(e.size() == 1 && e.at(0) == '*') ) e = "." + e;
}
DIR *dir;
struct dirent *ent;
struct stat sb;
std::map<int, std::string> r = {{999, "FAILED"}};
std::string temp;
int f = 0;
bool fd;
if ( (dir = opendir(p.c_str())) != NULL ){
r.erase (999);
while ((ent = readdir (dir)) != NULL){
temp = ent->d_name;
fd = temp.find(".") != std::string::npos? true : false;
temp = p + temp;
if (stat(temp.c_str(), &sb) == 0 && S_ISREG(sb.st_mode)){
if ( e.size() == 1 && e.at(0) == '*' ){
r[f] = temp;
f++;
} else {
if (e.size() == 0){
if ( fd == false ){
r[f] = temp;
f++;
}
continue;
}
if (e.size() > temp.size()) continue;
if ( temp.substr(temp.size() - e.size()) == e ){
r[f] = temp;
f++;
}
}
}
}
closedir(dir);
return r;
} else {
return r;
}
}
void printMap(auto &m){
for (const auto &p : m) {
std::cout << "m[" << p.first << "] = " << p.second << std::endl;
}
}
int main(){
std::map<int, std::string> k = getFile("./", "");
printMap(k);
return 0;
}
#include<iostream>
#include <dirent.h>
using namespace std;
char ROOT[]={'.'};
void listfiles(char* path){
DIR * dirp = opendir(path);
dirent * dp;
while ( (dp = readdir(dirp)) !=NULL ) {
cout << dp->d_name << " size " << dp->d_reclen<<std::endl;
}
(void)closedir(dirp);
}
int main(int argc, char **argv)
{
char* path;
if (argc>1) path=argv[1]; else path=ROOT;
cout<<"list files in ["<<path<<"]"<<std::endl;
listfiles(path);
return 0;
}
I have a .dat file containing 6 columns of N numbers like so:
-4.997740e-01 -1.164187e+00 3.838383e-01 6.395961e+01 -1.938013e+02 -4.310365e-02
-1.822405e+00 4.470735e-01 -2.691410e-01 -8.528020e+01 -1.358874e+02 -7.072167e-01
9.932887e-01 -2.157249e+00 -2.303825e+00 -5.508925e+01 -3.548236e+02 1.250405e+00
-1.871123e+00 1.505421e-01 -6.550555e-01 -3.254452e+02 -5.501001e+01 8.776851e-01
1.370605e+00 -1.028076e+00 -1.137059e+00 6.096598e+01 -4.472264e+02 -1.268752e+00
............ ............ ............ ............ ........... ...........
I want to write a code in C language where I extract the data from the file.dat and I assign the numbers of each column to a vector; for example:
V1=[-4.997740e-01;-1.822405e+00;9.932887e-01;-1.871123e+00;1.370605e+00];
and so on for all the 6 columns.
The only thing I know so far is that I need to start by doing something like this:
int main(){
FILE *fp;
fp=fopen("file.dat","r");
if (!fp){
printf("Error\n");
return 1;
}
return 0;
}
Does anyone know what I should do in order to accomplish my goal?
Try this
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#define MAX_ROW 256
int main()
{
FILE *file;
float data[MAX_ROW][6];
int index;
float *row;
file = fopen("file.dat", "r");
if (file == NULL)
{
perror("fopen()");
return 1;
}
index = 0;
row = data[0];
while (fscanf(file, "%f%f%f%f%f%f", &row[0], &row[1], &row[2], &row[3], &row[4], &row[5]) == 6)
{
printf("[%f;%f;%f;%f;%f;%f]\n", row[0], row[1], row[2], row[3], row[4], row[5]);
row = data[index++];
}
fclose(file);
return 0;
}
note that you could need to make data dynamically allocated to be able to resize it.
#include <iostream>
#include <conio.h>
#include <fstream>
using namespace std;
int main()
{
ifstream input("numbers.txt");
int a[500000];
if (input.is_open())
{
for (int i = 0; i <= 499999; i = i + 50000)
{
input >> a[i];
cout << a[i] << endl;
}
}
else
cout << "Could not open File" << endl << endl;
}
The file name "numbers.txt" is a simple txt file that contains exactly 500,000 integer numbers. Testing this code out on a small file of 100 integers it worked fine, but whenever I read this file is gave me the usual "file.exe has stopped working". Any idea why?