Read text file into char Array. C++ ifstream

Question

Im trying to read the whole file.txt into a char array. But having some issues, suggestions please =]

ifstream infile;
infile.open("file.txt");

char getdata[10000]
while (!infile.eof()){
  infile.getline(getdata,sizeof(infile));
  // if i cout here it looks fine
  //cout << getdata << endl;
}

 //but this outputs the last half of the file + trash
 for (int i=0; i<10000; i++){
   cout << getdata[i]
 }

Or maybe someone can suggest a better way to store a text file into a char array. — nubme, Dec 07 '10 at 03:18
If you do this in anything but a toy app ensure you put protections against unlimited memory allocation. — seand, Dec 07 '10 at 03:21

score 5 · Answer 1 · answered Feb 05 '13 at 22:47

std::ifstream infile;
infile.open("Textfile.txt", std::ios::binary);
infile.seekg(0, std::ios::end);
size_t file_size_in_byte = infile.tellg();
std::vector<char> data; // used to store text data
data.resize(file_size_in_byte);
infile.seekg(0, std::ios::beg);
infile.read(&data[0], file_size_in_byte);

score 3 · Answer 2 · answered Nov 07 '13 at 02:03

3

Use std::string:

std::string contents;

contents.assign(std::istreambuf_iterator<char>(infile),
                std::istreambuf_iterator<char>());

answered Nov 07 '13 at 02:03

0x499602D2

87,005
36
149
233

1

...always had troubles memorizing this spell. Not quite intuitive. PS. Since OP requested a char array, `contents.c_str()` can be of use. – gluk47 Sep 07 '15 at 21:34

score 2 · Answer 3 · answered Dec 07 '10 at 03:52

2

You don't need to read line by line if you're planning to suck the entire file into a buffer.

char getdata[10000];
infile.read(getdata, sizeof getdata);
if (infile.eof())
{
    // got the whole file...
    size_t bytes_really_read = infile.gcount();

}
else if (infile.fail())
{
    // some other error...
}
else
{
    // getdata must be full, but the file is larger...

}

answered Dec 07 '10 at 03:52

Tony Delroy

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What if the file is bigger than `10000` chars? – Nawaz Apr 24 '14 at 05:00
.... and what you're going to do there? declare another char array of bigger size and read again? wrong, isn't it? – Nawaz Apr 25 '14 at 06:04

score 1 · Accepted Answer · answered Dec 07 '10 at 03:19

1

Every time you read a new line you overwrite the old one. Keep an index variable i and use infile.read(getdata+i,1) then increment i.

answered Dec 07 '10 at 03:19

tmiddlet

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2

`read(..., 1)` reads one character at a time... very inefficient. – Tony Delroy Dec 07 '10 at 03:53
infile.seekg(0,ios::end);int len = infile.peekg();infile.seekg(0,ios::beg);infile.read(getdata,len); – tmiddlet Dec 07 '10 at 14:09

score 1 · Answer 5 · answered Mar 14 '19 at 01:05

You could use Tony Delroy's answer and incorporate a little function to determine the size of the file, and then create the char array of that size, like this:

//Code from Andro in the following question: https://stackoverflow.com/questions/5840148/how-can-i-get-a-files-size-in-c

int getFileSize(std::string filename) { // path to file
    FILE *p_file = NULL;
    p_file = fopen(filename.c_str(),"rb");
    fseek(p_file,0,SEEK_END);
    int size = ftell(p_file);
    fclose(p_file);
    return size;
}

Then you can do this:

//Edited Code From Tony Delroy's Answer
char getdata[getFileSize("file.txt")];
infile.read(getdata, sizeof getdata);

if (infile.eof()) {
    // got the whole file...
    size_t bytes_really_read = infile.gcount();
}
else if (infile.fail()) {
    // some other error...
}

Read text file into char Array. C++ ifstream

5 Answers5

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