C++ :: Using Map And Writing Files

Dec 6, 2014

I'm using maps and writing files for the first time and I get a crazy compiler error when I try to compile the following code.

//map is named schedules
// saveSchedule() is a member of the Schedule class that writes a vector of objects to disk, or is supposed to
ofstream newFile("sched.txt");
map<string,Schedule>::iterator in;

[Code] .....

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C++ :: Reading And Writing Files?

Feb 20, 2015

I have to write a program that sorts names and grades from a file and output them to another.

For example:

Name: Peter Parker
Exam 1: 95
Exam 2: 90.625
Exam 3: 91.20

Name: Mary Smith
Exam 1: 65
Exam 2: 79.1234
Exam 3: 70.24

Becomes something like this in the output file:

Name: Parker, Peter
Average Score: 92.28
Grade: A

Name: Smith, Mary
Average Score: 71.45
Grade: C

I know I'm supposed to read the whole file, but I'm getting really confused on how to take the name of each student separately without recording Exam 1, 2, and 3. I'll be able to do the average score and grade on my own.

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C/C++ :: Reading And Writing Files

Jan 16, 2015

I'm messing around with reading and writing files. The first file creates a small txt file. Simple enough

#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main(){
string name;
string desc;

[Code] ....

It does what it should. It creates a text file "items.txt" .... It reads as such:

dagger,a dagger,15,10,0,1,3,1,0,0,0,1,0,0,0,0,0,1

The second file is meant to read the file and place the data back into the variables. This happens, but the data crams itself into the first variable, and the rest of them collect the trash that's in memory.

#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main() {
string name,desc;

[Code ....

I need to get "dagger" into name, "a dagger" into description, and each value with their perspective variable. I'm sure I need some type of "separator". Hopefully I can use the comma. Before it's over, I will have about a hundred items that will need to be read into a class of items.

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C :: Program Reading / Writing Files

Dec 10, 2013

program that I am working on. I want to use fgets() in my program so I could handle multiple words from a text(to be able to handle spaces). I get a weird result when running the program.

Code: #include <stdio.h>
#include <stdlib.h>
//#include "kim.h"
#include <string.h>
[code]....

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C++ :: Vectors And Reading / Writing Files

May 19, 2014

How to write the code for this with the following requirements:

download the text file weblog.txt

This file is an Apache web log taken from the web server for St. Mary's University. When a visitor goes to their web site, the visitor's browser makes a request to the web server to view a web page, which is a file residing on the server. Each time a page is requested by a browser, the web server records information about that request. This weblog.txt holds the details of some of those requests.

Create a non-member function to read each line of the web log file. This function must do error checking to ensure that the file is opened successfully, otherwise it must provide a message like "file not available" to the user.

Each line should then be stored in a vector such that the first element of the vector is the first line of the web log file. Because each element will hold an entire line from the file, the vector should be declared as a vector of strings.

Note: You must declare the vector in a function.

Create another non-member function to sort the contents of the vector. Make sure to pass the vector by reference or your sort will disappear when the function ends! Use the sort function with #include <algorithm> to do the sort; you do not have to write your own sort algorithm.

Create one more non-member function to write the contents of the vector to a file. Each element should be on its own line in the new file. The contents of the new file should look like the original input file once your program completes, but in sorted order.

Create a main function that calls all of your non-member functions.

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C/C++ :: Reading And Writing In Binary Files?

Jun 5, 2014

why I'm giving "Access violation reading location 0x336827B8" and also I was able to read my data but it's giving me weird stuff. I want to write the sorted grades and the average in a new disk file. so here's my code so far here's my code

#include "stdafx.h"
#include <iostream>
#include <fstream>
#include <string>
#include <iomanip>
using namespace std;
int avg(int sum, int size);
void swap(int *, int *);

[code]....

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C/C++ :: Writing Data To Files To Be Called Later?

Apr 5, 2014

I am trying to use myfile to create and write user data to a file [URL].

At the moment I only want to save as .txt so that I can open it to see that it wrote to file properly.

The main issue I get is that it says the file is not open when my program gets to the error checking at the very end, a few guides mentioned that if the file was not yet created a file with the specified name would be generated in the same folder as main on the hard drive. I did try creating the file as a notepad .txt file but it still read the error. Here is the snippet concerning the writing of the file:

void WriteToFile() {
if(myfile.is_open()) {
myfile.open("userdata.txt",ios::in);
myfile<<"User name: "<<NameFirst<<" "<<NameLast<<"

[Code] ....

it compiles fine with the rest of the program and everything runs smoothly, it just isn't writing to a file.I have included <string>, <iostream> and <fstream>.

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C++ :: Writing / Reading String Objects To / From Files

Jul 7, 2013

I am using the code below to write a single instance of object "Employee" to a file in Binary mode. The write part seems to work fine, however when I try to read the single employee object from the file into memory I get a double free or corruption error.

I think this has to do with the fact that I am using a string data member in the Employee class but I don't understand what is going wrong. I have read that strings can vary in length and use dynamic memory allocation but if I write a single employee object to a file with data member 'name' equal to "John", it should be the exact same size when I read it back in right?

The code below works with no issues when I omit the string data member. Why is that? Where is the memory for the string object being "double released" when I read the employee object back into memory from the file?

I am using Linux Mint 15, Eclipse June and GCC 4.7.3 with the -std=c++11 option.

#include <iostream>
#include <fstream>
#include <string>

[Code].....

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C/C++ :: Writing Multiple Files In Nested Loop?

Jun 3, 2014

I would like to do something like this:

for (int i=0; i<5; i ++)
{
for (int j=0; j<5; j++)
{
//* CREATE A NEW FILE FOR WRITING * //
}
}

I don't know how to create a new file that doesn't get overwritten each time the loop runs.

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C++ :: Composition - Writing Programs In Multiple Files

Oct 23, 2012

So lately I've been writing multiple header and cpp files and I would always the same error when I finally #include headers in my main.cpp. This error

Code:
undefined reference to `...`

On Youtube videos I see people doing this and their work magically compiles correctly. I found out that when I #include the headers' cpp files instead, my programs would compile. I use Code::Blocks with GNU GCC compiler.

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Visual C++ :: Enable Writing To And Reading From Files - Unresolved External Symbol

May 13, 2013

Perhaps this can be a very popular error,

Code:

#include <stdio.h>
#include <tchar.h>
#include <iostream>
#include <string>
#include <fstream>// enable writing to and reading from files
#include <cstdlib>
#include <time.h>
using namespace std;
class Person {

[Code] .....

Error list:

Code:

Error 1 error LNK2019: unresolved external symbol "void __cdecl saveperson(void)" (?saveperson@@YAXXZ) referenced in function _main H:Cry_DevProgrammingC++Using_class_ in_ c++Using_class_ in_ c++Using_class_ in_ c++.obj
Error 2 error LNK2019: unresolved external symbol "void __cdecl displayperson(void)" (?displayperson@@YAXXZ) referenced in function _main H:Cry_DevProgrammingC++Using_class_ in_ c++Using_class_ in_ c++Using_class_ in_ c++.obj
Error 3 error LNK2019: unresolved external symbol "void __cdecl editperson(void)" (?editperson@@YAXXZ) referenced in function _main H:Cry_DevProgrammingC++Using_class_ in_ c++Using_class_ in_ c++Using_class_ in_ c++.obj
Error 4 error LNK1120: 3 unresolved externals H:Cry_DevProgrammingC++Using_class_ in_ c++DebugUsing_class_ in_ c++.exe 1

What I can do to fit this problem?

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C :: Program To Hide Files Behind Other Files Using Alternate Data Streams

Apr 5, 2013

I am writing a program to hide files behind other files using Alternate Data Streams in Windows NTFS file systems.

The program is as follows:

Code:

#include <stdio.h>
#include <stdlib.h>
int main(void){
char hostfile[75], hiddenfile[75], hiddenFileName[15] ;
printf("Enter the name(with extension) and path of the file whose behind you want to hide another file: ");
scanf("%75s", hostfile);

[Code]...

The complier is showing error as "Extra Perimeter in call to system" but I am not getting where?

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C++ :: Display Last 1000 Lines From Multiple Text Files (log Files)

Jan 16, 2014

I am writing a piece of code that requires me to display the last 1000 lines from a multiple text files (log files). FYI, I am running on Linux and using g++.

I have a log file from which - if it contains more than 1000 lines, I need to display the last 1000 lines. However, the log file could get rotated. So, in case where the current log file contains less than 1000 lines, I have to go to older log file and display the remaining. For e.g., if log got rotated and new log file contains 20 lines, I have to display the 980 lines from old log file + 20 from current log files.

What is the best way to do this? Even an outline algorithm will work.

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Visual C++ :: Should Precompiled Header Files Also Be Included In Source Header Files?

Sep 16, 2013

When including a header file in stdafx.h, should that file still be included in the source file where it is actually used?

If it is included in both places, is the one in the source file ignored?

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C/C++ :: Writing Int Value To UART?

Mar 17, 2014

I'm working on a 10 week project, and this is a small issue that I can't fix myself.

///////////////////////////////////////////
/* WRITE SINGLE CHAR */
///////////////////////////////////////////
void LCD_Write(unsigned char c) {
while(!(UCSR1A & (1<<UDRE1))); // 0x20 (1<<UDRE0)
UDR1 = c;
Delay(5);

[code]....

This project is a Atmega 2560 connected to a serial GLCD screen.I've got serial communication working perfectly.Now as you can see I wrote a function that sends 1 single character to the UDR1.I wrote a function that uses this first function for sending entire words (strings).All of this works great.

Next challenge is writing a "int byte" to the GLCD screen.In this case the variable "voltage" has a value of 100.I'd like to write that 100 to the serial display via the uart.But whenever I do this the screen reads this 100 as a ascii decimal number... (= d)

I've tried things like

LCD_PrintStr("voltage"); (Result: The word voltage shows up on the screen)
LCD_Write(voltage); (Result: write ascii letter for dec 100 (= d ))

[URL]

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C++ :: Writing New Line To File

Sep 9, 2014

I am executing below sample program

Code: #include<iostream.h>
#include <fstream.h>
using namespace std;
int main()

[Code]......

when i am counting the lines using wc command it is giving 1 instead of 2.

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C++ :: Reading And Writing Bit To A File

Nov 3, 2014

I'm writing a program using Huffman algorithm to compress text file. I have tested my program by just printing the printing ASCII character to file and it worked fine. However, now I have to implement using bits and my program doesn't work. It seems like I'm not reading or writing the right bits. Here is the result of my testing:In the input file I put abc the input file to compress it. Then I uncompress it the out out is aaa. Below is a snippet of how I read and write bits

Code:
class BitInput {
istream& in; // the istream to delegate to
char buf; // the buffer of bits
int nbits; public:

BitInputStream(istream& s) : in(s), buf(0), bufi(8) { }

[Code] ....

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C# :: Writing To A File (Not Replacing)

Dec 11, 2011

I have a question about an issue I am having on my final project. Within my ItemEntry.cs form, I am trying to get the application to append the already existing .txt file, rather than prompt the user to replace it. I can't seem to get the StreamWriter and FileStream to allow the user to write to the file.

Code:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;

[Code] .....

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C :: Writing A Struct To A File

Sep 28, 2013

I am trying to write a structure to a file. Example say the structure has two variables x and y . I want to write a function which modifies these variables and stores the modified version on a file. Such that next time I call the function . it has the values from the previous write. Here's an example of my code .

Code:
// initialize the structure struct->x = 0, struct->y = 0
File *fp = fopen("filename", "r+");
struct MYSTRUCT mystruct = (struct MYSTRUCT*)malloc(sizeof(MYSTRUCT))

//check
fread (mystruct, sizeof(MYSTRUCT), 1, fp);

// do some calculations.
fwrite(mystruct, sizeof(MYSTRUCT), 1, fp);
fclose(fp)

//return some value
}

The problem is that each time I run the program it shows the initialized value of the variables and not the value from last write. I guess the write isn't successful because when I open in w+ mode. i get the error file could not be opened and then i have to delete the file and re create it....

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C :: Writing Numbers In Letters?

Jan 26, 2013

Code:
#include<stdio.h>
#include<string.h>
#define a 9
#define b 9
#define c 3
int main() {

[Code] .....

In practice section there was a challenge to print up numbers in letters up to billion including negatives I didn't look at the solution and came up with this but it is getting difficult after this point....

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C :: File Reading And Writing

Sep 19, 2013

I have a text file containing 500 signed decimal numbers. My task is to read each entry and convert into a 16-bit 2's complement representation (binary number) and write into the another text file.

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C :: Writing New Line In A File?

Oct 4, 2014

I have a problem writing new line in a file. So far, this is my code.

Code:

fprintf(f, (ctime(&mytime)));
fprintf(f, "%s %s %d %d", item, brand, price, amount);
fprintf(f, "
");
fclose(f);

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C :: Reading And Writing To File

Mar 19, 2013

Code:
#include <stdio.h>
struct hardware{
int recNum;
char toolName[30];
int quant;
double cost;

[Code] .....

I'm having issues with my functions working properly. I'm not sure where I'm going wrong with them and if i'm using the correct mode for the fopen.

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C++ :: Writing Speech To Text?

Sep 13, 2013

How to write speech to text application? Without any plugin all code by myself like Google or Microsoft SAPI or Apple Siri

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C++ :: How To Start Writing Game App

Oct 23, 2013

How do i start writing Gaming app using C++. What is the environment required. I have mingw compiler installed on Windows8.

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C++ :: Writing Float Value To File

Oct 11, 2014

I'm trying to write the value of xcord to the file, but it's come out as jiberish like š™ for some reason.

#include <iostream>
#include <Windows.h>
using namespace std;

[code]....

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