How to read a list of filenames from a text file and open them in C++?

问题

I have a list of files stored in a text file. I read the file line by line and store them in a string array. The file list looks like this:

04_02_1310.csv
04_03_1350.csv
04_04_0421.csv
04_05_0447.csv

and so on. Let's call my string array

filelist[i]

Assuming I am trying the open the first file in the list:

inputFile.open(filelist[0].c_str()); // This cannot open file

the file cannot be opened. If i place the file name in quotation marks, everything works out fine:

inputFile.open("04_02_1310.csv"); // This works perfectly

if i print the contents of filelist[i], then it works fine as well:

cout << filelist[0] << endl; // This outputs 04_02_1310.csv on screen.

Can somebody tell me what is wrong with the approach above? This is driving me crazy for the last 2 days, and I am about the enter everything manually just to get it done (100+ files one after another).

I am also open to any other way to do this simple task.

Thanks!!!

EDIT: I am adding a relevant portion of the code if you would like to see how it is implemented:

#include <cstdlib>
#include <iostream>
#include <time.h>
#include <string>
#include <sstream>
#include <fstream>
#include <vector>
#include <algorithm>
#include <iterator>

using namespace std;

//Declarations for I/O files
ifstream inputFile;

//Declare other variables (forgot to add these in my previous EDIT, sorry)
int number_of_files;
string line;
string *filelist = NULL;

//Open file list and count number of files
inputFile.clear();
inputFile.open("filelist.txt", ios::in);

//exit and prompt error message if file could not be opened
if (!inputFile){
    cerr << "File list could not be opened" << endl;
    exit(1);
}// end if

// count number of lines in the data file and prompt on screen
number_of_files = 0;

while (getline(inputFile, line))        
    number_of_files++;

cout << "Number of files to be analyzed: " << number_of_files << endl;

filelist = new string[number_of_files];
inputFile.close();

//Re-open file list and store filenames in a string array
inputFile.clear();
inputFile.open("filelist.txt", ios::in);

//exit and prompt error message if file could not be opened
if (!inputFile){
    cerr << "File list could not be opened" << endl;
    exit(1);
}// end if

// store filenames
i = 0;
while (getline(inputFile, line)){
    filelist[i] = line;
    //cout << filelist[i] << endl;
    i = i + 1;
}        

inputFile.close();

//open first file in the list, I deleted the loop to focus on the first element for now

inputFile.clear();
inputFile.open(filelist[0].c_str(), ios::in);

//exit and prompt error message if file could not be opened
if (!inputFile){
    cerr << "Data file could not be opened" << endl;
    exit(1);
}// end if

The output is:

Data file could not be opened

Thanks again!

回答1:

It is possible that there still is the '\n' char (or EOF,'\0' ) from your textfile in that string, you should try checking if the strings are "clean".

回答2:

I am also open to any other way to do this simple task.

#include <cstdlib>
#include <iostream>
#include <time.h>
#include <string>
#include <sstream>
#include <fstream>
#include <vector>
#include <algorithm>
#include <iterator>

using namespace std;

int main () {

  std::ifstream inputFile("filelist.txt");
  std::vector<std::string> fileList;
  std::string line;

  if(!inputFile) {
    std::cerr << "File list could not be opened\n";
    return 1;
  }

  while(std::getline(inputFile, line)) {
    fileList.push_back(line);
  }

  std::cout << "Number of files to be analyzed: " << fileList.size() << "\n";

  std::vector<std::string>::const_iterator it(fileList.begin());
  std::vector<std::string>::const_iterator end(fileList.end());
  for(;it != end;++it) {
    std::ifstream inputTxt(it->c_str());

    if(!inputTxt) {
      std::cerr << "Data file could not be opened:" << *it << "\n";
      return 1;
    }
    while(std::getline(inputTxt, line)) {
      std::cout << line << "\n";
    }
  }
}

回答3:

I suggest to use a more 'C++ - ish' approach, although different from the elegant solution posted by Blood:

int main()
{
    std::vector<std::string> fileList;

    // ...

    std::ifstream inputFile("filelist.txt");

    // ...

    std::string line;
    while(inputFile >> line)
        filelist.push_back(line);

    inputFile.close();

    // ...

    for(size_t t = 0; t < filelist.size(); t++)
    {
        std::ifstream dataFile(filelist[t].c_str());

        // ...

        dataFile.close();
    }
}

来源：https://stackoverflow.com/questions/11474038/how-to-read-a-list-of-filenames-from-a-text-file-and-open-them-in-c

标签

c++

string

file-io

ifstream