I am trying to read all the characters in a file into an array. Assuming all variables are declared, why are all the characters not being read into my array. When I output some of the characters in the "storeCharacters[]" array, garbage is being returned. Please help.
This is my function:
void countChars(ifstream& input, char storeCharacters[])
{
int i = 0;
while( !input.eof() )
{
input.get(storeCharacters[i]);
i++;
}
}
After the while loop try adding storeCharacters[i] = '\0' to null terminate the string.
The easy fix to your problem if you know the maximum size of your file, then just set your array to have that size and initialize it with \0.
let's say the maximum characters count in your file is 10000.
#define DEFAULT_SIZE 10000
char storeCharacters[DEFAULT_SIZE];
memset (storeCharacters,'\0',DEFAULT_SIZE) ;
The below post should be the correct way to read a file using a buffer it has memory allocation and all what you need to know :
Correct way to read a text file into a buffer in C?
#include <iostream>
#include <fstream>
#include <iomanip>
#include <string>
#include <cstdlib>
using namespace std;
void getFileName(ifstream& input, ofstream& output) //gets filename
{
string fileName;
cout << "Enter the file name: ";
cin >> fileName;
input.open(fileName.c_str());
if( !input )
{
cout << "Incorrect File Path" << endl;
exit (0);
}
output.open("c:\\users\\jacob\\desktop\\thomannProj3Results.txt");
}
void countWords(ifstream& input) //counts words
{
bool notTrue = false;
string words;
int i = 0;
while( notTrue == false )
{
if( input >> words )
{
i++;
}
else if( !(input >> words) )
notTrue = true;
}
cout << "There are " << i << " words in the file." << endl;
}
void countChars(ifstream& input, char storeCharacters[], ofstream& output) // counts characters
{
int i = 0;
while( input.good() && !input.eof() )
{
input.get(storeCharacters[i]);
i++;
}
output << storeCharacters[0];
}
void sortChars() //sorts characters
{
}
void printCount() //prints characters
{
}
int main()
{
ifstream input;
ofstream output;
char storeCharacters[1000] = {0};
getFileName(input, output);
countWords(input);
countChars(input, storeCharacters, output);
return 0;
}
Related
in my program I am attempting to input characters from a .txt file and assign them to a 2D Char array to form a Maze. The expected outcome of this code is:
xxxxxxx
xA...Bx
xxxxxxx
However I am instead warned that Column is greater than size (defined as 30) when I believe it should be 0 at the start of every loop. No matter what Column is equal to Size and im not sure why. I've included the code below. I am beginner programmer so if you have any advice could you please make it as simple as possible.
Many thanks,
Ben
#include<fstream>
#include<iostream>
#include<string>
#include <vector>
//Maze Size
#define SIZE 30
using namespace std;
void readMaze(string fileName);
void inputMaze();
int main()
{
inputMaze();
}
void readMaze(string fileName)
{
int rows;
int columns = 0;
//vector<vector<char>> maze;
char maze[SIZE][SIZE];
ifstream input(fileName);
char data;
while (input.get(data)) //While loop used to store each individual data to the string.
{
for (int rows = 0; rows < 20; rows++)
{
columns = 0;
while (data != '\n')
{
if (rows > SIZE)
{
cout << "ROWS GREATER THAN SIZE";
break;
}
else if (columns > SIZE)
{
cout << "COLUMNS GREATER THAN SIZE";
break;
}
else
{
maze[rows][columns] = data;
columns++;
data = input.get();
}
}
data = input.get();
}
}
cout << "The Maze being solved is: " << endl;
cout << maze << endl;
input.close();
}
void inputMaze()
{
string userinput;
cout << "Plese input a .txt file name" << endl;
cin >> userinput; //User inputs the name of a .txt file --> goes to readMaze()
readMaze(userinput);
}
rows is used uninitialized in readMaze so the program has undefined behavior. Also, cout << maze << endl; makes the program have undefined behavior by reading out of bounds.
Consider making maze a std::vector<std::vector<char>> or even a std::vector<std::string> to make it simpler.
Example:
#include <algorithm>
#include <fstream>
#include <iostream>
#include <iterator>
#include <sstream>
#include <string>
#include <vector>
std::vector<std::string> readMaze(std::istream& input) {
std::vector<std::string> maze;
std::string line;
while(std::getline(input, line)) { // read a complete line at a time
maze.push_back(line); // and save it in the vector
}
return maze;
}
void inputMaze() {
std::string userinput;
std::cout << "Plese input a .txt file name\n";
if(std::cin >> userinput) {
std::ifstream is(userinput);
if(is) {
auto maze = readMaze(is);
std::cout << "The Maze being solved is:\n";
std::copy(maze.begin(), maze.end(),
std::ostream_iterator<std::string>(std::cout, "\n"));
}
// the file will be closed automatically when "is" goes out of scope
}
}
int main() {
inputMaze();
}
#include <iostream>
#include <iomanip>
#include <cstdlib>
#include <fstream>
using namespace std;
void make_array(ifstream& num, int (&array)[50]);
int main()
{
ifstream file; // variable controlling the file
char filename[100]; /// to handle calling the file name;
int array[50];
cout << "Please enter the name of the file you wish to process:";
cin >> filename;
cout << "\n";
file.open(filename);
if (file.fail()) {
cout << "The file failed to open.\n";
exit(1);
} else {
cout << "File Opened Successfully.\n";
}
make_array(file, array);
file.close();
return (0);
}
void make_array(ifstream& num, int (&array)[50])
{
int i = 0; // counter variable
while (!num.eof() && i < 50) {
num >> array[i];
i = i + 1;
}
for (i; i >= 0; i--) {
cout << array[i] << "\n";
}
}
I am trying to read values from a file to an array using fstream. When I try to display the contents of the array, I get 2 really big negative numbers, and then the contents of the file.
Any ideas what I did wrong?
Your use of num.get(array[i]) doesn't match any of its signatures. See get method description. What you want is this:
array[i] = num.get();
As discussed in the comments, you try to read an integer which is encoded as text. For this, you need to use operator>> (which reads any type encoded as string) instead of get (which reads a single byte):
num >> array[i];
The input file contains 14 state initials (TN,CA,NB,FL,etc..) that is to be rad into the array. The code below clears compiler but when i tell the program the filename it shoots out a bunch of blank spaces with two spaces containing some fuzz and a third contain a '#' symbol. i assume the problem is with my function not entirely sure what specifically though any help greatly appreciated!
input file set up with state initials one on top of the other:
TN
PA
KY
MN
CA
and so on
void readstate( ifstream& input, string []);
int main()
{
string stateInitials[14];
char filename[256];
ifstream input;
cout << "Enter file name: ";
cin >> filename;
input.open( filename );
if ( input.fail())
{
cout << " file open fail" << endl;
}
readstate ( input, stateInitials);
input.close();
return (0);
}
void readstate ( ifstream& input, string stateInitials[])
{
int count;
for ( count = 0; count <= MAX_ENTRIES; count++)
{
input >> stateInitials[count];
cout << stateInitials[count] << endl;
}
}
You are treating a character array as though it were a string array.
While you can hack put the strings next to each other inside the same char array, that is not the standard way it is done. Here is a modified version of your code, which creates one char[] to hold each initial.
#include <iostream>
#include <fstream>
#include <string>
#include <stdlib.h>
#include <string.h>
#define MAX_ENTRIES 14
using namespace std;
void readstate( ifstream& input, char* []);
int main()
{
char** stateInitials = new char*[14];
char filename[256];
ifstream input;
cout << "Enter file name: ";
cin >> filename;
input.open( filename );
if ( input.fail())
{
cout << " file open fail" << endl;
}
readstate ( input, stateInitials);
// After you are done, you should clean up
for ( int i = 0; i <= MAX_ENTRIES; i++) delete stateInitials[i];
delete stateInitials;
return (0);
}
void readstate ( ifstream& input, char* stateInitials[])
{
int count;
string temp_buf;
for ( count = 0; count <= MAX_ENTRIES; count++)
{
stateInitials[count] = new char[3];
input >> temp_buf;
memcpy(stateInitials[count], temp_buf.c_str(), 3);
cout << stateInitials[count] << endl;
}
}
The problem is that file won't be read...Apparently there's a problem with an array but I don't really know how fix this issue...I'm a beginner to C++ 'arrays' and 'strings'...
My file should read the code, then translate the file, then output the text into a new file..
#include <iostream>
#include <iomanip>
#include <string>
#include <sstream>
#include <fstream>
#include <math.h>
#include <stdio.h>
#include <string>
#include <string.h>
using namespace std;
int main()
{
// Declarations
string reply;
string inputFileName;
ifstream inputFile;
ofstream outFile;
char character;
cout << "Input file name: ";
getline(cin, inputFileName);
// Open the input file.
inputFile.open(inputFileName.c_str());
// Check the file opened successfully.
if ( ! inputFile.is_open()) {
cout << "Unable to open input file." << endl;
cout << "Press enter to continue...";
getline(cin, reply);
return 1;
}
// This section reads and echo's the file one character (byte) at a time.
while (inputFile.peek() != EOF) {
inputFile.get(character);
//cout << character;
//Don't display the file...
char cipher[sizeof(character)];
//Caesar Cipher code...
int shift;
do {
cout << "enter a value between 1-26 to encrypt the text: ";
cin >> shift;
}
while ((shift <1) || (shift >26));
int size = strlen(character);
int i=0;
for(i=0; i<size; i++)
{
cipher[i] = character[i];
if (islower(cipher[i])) {
cipher[i] = (cipher[i]-'a'+shift)%26+'a';
}
else if (isupper(cipher[i])) {
cipher[i] = (cipher[i]-'A'+shift)%26+'A';
}
}
cipher[size] = '\0';
cout << cipher << endl;
}
cout << "\nEnd of file reached\n" << endl;
// Close the input file stream
inputFile.close();
cout << "Press enter to continue...";
getline(cin, reply);
return 0;
}
To make it short: You're on c++ so just don't use the whole C stuff.
Don't use character arrays, use std::string
Don't use islower(char) but use std::islower(char,locale)
Don't use C-style arrays but std::array (compile time constant size) or std::vector (dynamic size)
You'll want to have it more like this:
#include <string>
#include <fstream>
#include <iostream>
#include <stdexcept>
#include <locale>
int main (void)
{
std::string input_filename;
std::cout << "Input file name: ";
std::getline(std::cin, input_filename);
unsigned int shift;
do
{
std::cout << "Enter a value between 1-26 to encrypt the text: ";
std::cin >> shift;
}
while ((shift == 0) || (shift > 26));
try
{
std::string filestring;
std::ifstream input(input_filename, std::ios_base::in);
if (input)
{
input.seekg(0, std::ios::end);
filestring.reserve(input.tellg());
input.seekg(0, std::ios::beg);
filestring.assign
(std::istreambuf_iterator<char>(input),
std::istreambuf_iterator<char>());
}
else
{
std::string error_string("Reading failed for: \"");
error_string.append(input_filename);
error_string.append("\"");
throw std::runtime_error(error_string);
}
std::string result;
result.reserve(filestring.size());
std::locale const loc;
for (auto character : filestring)
{
char const shifter(std::islower(character, loc) ? 'a' : 'A');
result.push_back((character-shifter+shift)%26+shifter);
}
std::cout << result << std::endl;
}
catch (std::exception & e)
{
std::cout << "Execution failed with an exception: " << std::endl;
std::cout << e.what() << std::endl;
}
}
This solution requires C++11 support. If you do not have C++11 you can replace the loop with:
size_t const N(filestring.length());
for (size_t i(0u); i<N; ++i)
{
char const shifter(std::islower(filestring[i], loc) ? 'a' : 'A');
result.push_back((filestring[i]-shifter+shift)%26+shifter);
}
From looking at your code, "character" is declared as a char which means it can only store one byte of information. Yet later on you start using it as if it was an array of characters.
You are also declare "cipher" as a char array that you manual manage like a string which is error prone. The real issue however is that you're mixing C-like code in C++. In other words, the way your code is written isn't considered idiomatic C++.
Pixelchemist already went over the important points so I'll just present a minimal refactored working example of your above code:
#include <iostream>
#include <string>
#include <fstream>
#include <stdlib.h>
using namespace std;
int main()
{
string filename;
cout << "enter input file: ";
cin >> filename;
ifstream inputFile( filename.c_str() );
string plaintext;
do
{
plaintext += inputFile.get();
}while(inputFile);
cout << plaintext << endl;
string &ciphertext = plaintext;
//Caesar Cipher code...
int shift = rand() % 26 + 1;
for(size_t i = 0; i < ciphertext.size(); ++i)
{
if (islower(ciphertext[i])) {
ciphertext[i] = (ciphertext[i] - 'a' + shift) % 26 + 'a';
}
else if (isupper(ciphertext[i])) {
ciphertext[i] = (ciphertext[i] - 'A' + shift) % 26 + 'A';
}
}
cout << ciphertext << endl;
}
You'll notice in the refactor that I've done away with char and char[] arrays altogether and replaced it with std::string. I'm also performing the cipher operation inplace on the plaintext input. This is done by making a reference alias to plaintext called ciphertext for readability. Also in my example, the shift is done randomly for prototyping but you should change it to take it as a user input instead.
You are working with a single char, thats e.g. just one letter or a number. So the whole thing with size handling is useless, because the size is always 1. You probably should use const char*. But then you can't use filestream.get() at all, because it only returns a single char (not and cstring aka const char*).
And you can use fstream.get() as condition for the loop, so you don't need to ask for the eof flag.
char my_char;
std::ifstream infstream("filename.txt");
if(!infstream.isopen())
return -1;
while(infstream.get(my_char) {
//do some stuff
}
or
std::string my_string;
std::ifstream infstream("filename.txt");
if(!infstream.isopen())
return -1;
while(infstream >> my_string) {
//do some stuff
}
for dynamic arrays in C++ use std::vector or std::list or ... one of the other STL containers, so you don't have to waste your time on memory management and using static sized arrays.
And std::string is the way to go for strings in C++. It is something similar to the STL containers, but just for char's.
I'm a physics PhD student with some experience coding in java, but I'm trying to learn C++.
The problem I'm trying to solve is to read in data from a .txt file and then output all the numbers > 1000 in one file and all those <1000 in another.
What I need help with is writing the part of the code which actually reads in the data and saves it to an array. The data itself is only separated by a space, not all on a new line, which is confusing me a bit as I don't know how to get c++ to recognise each new word as an int. I have canabalised some code I have got from various sources online-
#include <iostream>
#include <string>
#include <fstream>
#include <cstring>
#include<cmath>
using namespace std;
int hmlines(ifstream &a) {
int i=0;
string line;
while (getline(a,line)) {
cout << line << endl;
i++;
}
return i;
}
int hmwords(ifstream &a) {
int i=0;
char c;
a >> noskipws >> c;
while ((c=a.get()) && (c!=EOF)){
if (c==' ') {
i++;
}
}
return i;
}
int main()
{
int l=0;
int w=0;
string filename;
ifstream matos;
start:
cout << "Input filename- ";
cin >> filename;
matos.open(filename.c_str());
if (matos.fail()) {
goto start;
}
matos.seekg(0, ios::beg);
w = hmwords(matos);
cout << w;
/*c = hmchars(matos);*/
int RawData[w];
int n;
// Loop through the input file
while ( !matos.eof() )
{
matos>> n;
for(int i = 0; i <= w; i++)
{
RawData[n];
cout<< RawData[n];
}
}
//2nd Copied code ends here
int On = 0;
for(int j =0; j< w; j++) {
if(RawData[j] > 1000) {
On = On +1;
}
}
int OnArray [On];
int OffArray [w-On];
for(int j =0; j< w; j++) {
if(RawData[j]> 1000) {
OnArray[j] = RawData[j];
}
else {
OffArray[j] = RawData[j];
}
}
cout << "The # of lines are :" << l
<< ". The # of words are : " << w
<< "Number of T on elements is" << On;
matos.close();
}
But if it would be easier, i'm open to starting the whole thing again, as I don't understand exactly what all the copied code is doing. So to summarise, what I need is it to-
Ask for a filepath in the console
Open the file, and store each number (separated by a space) as an element in a 1D array
I can manage the actual operations myself I think, if I could just get it to read the file the way I need.
Thanks very much
Using C++11 and the Standard Library makes your task fairly simple. This uses Standard Library containers, algorithms, and one simple lambda function.
#include <algorithm>
#include <iostream>
#include <iterator>
#include <fstream>
#include <string>
#include <vector>
int main()
{
std::string filename;
std::cout << "Input filename- ";
std::cin >> filename;
std::ifstream infile(filename);
if (!infile)
{
std::cerr << "can't open " << filename << '\n';
return 1;
}
std::istream_iterator<int> input(infile), eof; // stream iterators
std::vector<int> onvec, offvec; // standard containers
std::partition_copy(
input, eof, // source (begin, end]
back_inserter(onvec), // first destination
back_inserter(offvec), // second destination
[](int n){ return n > 1000; } // true == dest1, false == dest2
);
// the data is now in the two containers
return 0;
}
Just switch the type of variable fed to your fistream, created from new std:ifstream("path to file") into a int and c++ will do the work for you
#include <fstream> //input/output filestream
#include <iostream>//input/output (for console)
void LoadFile(const char* file)
{
int less[100]; //stores integers less than 1000(max 100)
int more[100]; //stores integers more than 1000(max 100)
int numless = 0;//initialization not automatic in c++
int nummore = 0; //these store number of more/less numbers
std::ifstream File(file); //loads file
while(!file.eof()) //while not reached end of file
{
int number; //first we load the number
File >> number; //load the number
if( number > 1000 )
{
more[nummore] = number;
nummore++;//increase counter
}
else
{
less[numless] = number;
numless++;//increase counter
}
}
std::cout << "number of numbers less:" << numless << std::endl; //inform user about
std::cout << "number of numbers more:" << nummore << std::endl; //how much found...
}
This should give you an idea how should it look like(you shoudnt use static-sized arrays tough) If you got any probs, comment back
Also, please try to make nice readable code, and use tabs/ 4 spaces.
even though its pure C, this might give you some hints.
#include <stdio.h>
#include <stdlib.h>
#include "string.h"
#define MAX_LINE_CHARS 1024
void read_numbers_from_file(const char* file_path)
{
//holder for the characters in the line
char contents[MAX_LINE_CHARS];
int size_contents = 0;
FILE *fp = fopen(file_path, "r");
char c;
//reads the file
while(!feof(fp))
{
c = fgetc(fp);
contents[size_contents] = c;
size_contents++;
}
char *token;
token = strtok(contents, " ");
//cycles through every number
while(token != NULL)
{
int number_to_add = atoi(token);
//handle your number!
printf("%d \n", number_to_add);
token = strtok(NULL, " ");
}
fclose(fp);
}
int main()
{
read_numbers_from_file("path_to_file");
return 0;
}
reads a file with numbers separated by white space and prints them.
Hope it helps.
Cheers