so guys i have to create 5 job objects from the information from a text file which looks like this
A 0 3
B 2 6
C 4 4
D 6 5
E 8 2
the left column is its name, the next is arrival time, and the final one is the duration
this is what i have right now
#include <iostream>
#include <fstream>
#include "Job.hpp"
using namespace std;
int main(int argc, const char * argv[]) {
string fileinfo;
string programname;
//gets Jobs.txt from commandline
programname.append(argv[1]);
Job jobs[5];
fstream afile;
//reads in from the file to create job objects
afile.open(programname);
if(afile.fail()){
cout <<"file could not be opened " << programname <<endl;
}
while(!afile.eof())
{
getline(afile,fileinfo);
int i = 0;
//cout <<fileinfo[0] <<endl;//gets next letter
//cout <<fileinfo[2] <<endl;//gets next arrival time
//cout << fileinfo[4] <<endl;//gets next duration time
jobs[i].setletter(fileinfo[0]);
jobs[i].setarrivaltime(fileinfo[2]);
jobs[i].setduration(fileinfo[4]);
i++;
}
afile.close();
cout << jobs[1].getletter() <<endl;
cout << jobs[2].getletter() <<endl;
cout << jobs[3].getduration() <<endl;
right now when i go in and print out the values in my different objects(like at the bottom of the code)after i close the file they all contain the information from the first line of the file.
i dont know why because technically i increase 'i' after i set all the values of the job and then fileinfo gets the nextline of the file, so this to me seems like it should work.
But like the values i get from those 3 couts at the bottom the results are
A
A
0
the Job class
Job::Job(){}
Job::Job(char let, int arrive, int dura){
letter = let;
arrivaltime = arrive;
duration = dura;
}
and it also has all its get and sets defined
so can u guys please help me be able to read in from the file correctly and create my object array
int i = 0;
Each time through the loop, i gets initialized to zero. Immediately after initializing i to 0, your code does this:
jobs[i].setletter(fileinfo[0]);
jobs[i].setarrivaltime(fileinfo[2]);
jobs[i].setduration(fileinfo[4]);
i will always be zero, here. This is what you're seeing. Your computer will always do exactly what you tell it to do, instead of what you want it to do. This is a good rule of thumb for you to keep in mind, going forward.
i++;
This doesn't matter, because on the next iteration of the while loop, i will be initialized to 0 again. See above.
while(!afile.eof())
And, this is going to be your second bug, also, which you will immediately discover after fixing your first bug (initialize i before the loop, not inside it).
Related
I began learning strings yesterday and wanted to manipulate it around by filling it with a text from a text file. However, upon filling it the cstring array only prints out the last word of the text file. I am a complete beginner, so I hope you can keep this beginner friendly. The lines I want to print from the file are:
"Hello World from UAE" - First line
"I like to program" - Second line
Now I did look around and eventually found a way and that is to use std::skipary or something like that but that did not print it the way I had envisioned, it prints letter by letter and skips each line in doing so.
here is my code:
#include <fstream>
#include <iostream>
#include <cstring>
#include <cctype>
using namespace std;
int main() {
ifstream myfile;
myfile.open("output.txt");
int vowels = 0, spaces = 0, upper = 0, lower = 0;
//check for error
if (myfile.fail()) {
cout << "Error opening file: ";
exit(1);
}
char statement[100];
while (!myfile.eof()) {
myfile >> statement;
}
for (int i = 0; i < 30; ++i) {
cout << statement << " ";
}
I'm not exactly sure what you try to do with output.txt's contents, but a clean way to read through a file's contents using C++ Strings goes like this:
if (std::ifstream in("output.txt"); in.good()) {
for (std::string line; std::getline(in, line); ) {
// do something with line
std::cout << line << '\n';
}
}
You wouldn't want to use char[] for that, in fact raw char arrays are hardly ever useful in modern C++.
Also - As you can see, it's much more concise to check if the stream is good than checking for std::ifstream::fail() and std::ifstream::eof(). Be optimistic! :)
Whenever you encounter output issues - either wrong or no output, the best practise is to add print (cout) statements wherever data change is occurring.
So I first modified your code as follows:
while (!myfile.eof()) {
myfile >> statement;
std::cout<<statement;
}
This way, the output I got was - all lines are printed but the last line gets printed twice.
So,
We understood that data is being read correctly and stored in statement.
This raises 2 questions. One is your question, other is why last line is printed twice.
To answer your question exactly, in every loop iteration, you're reading the text completely into statement. You're overwriting existing value. So whatever value you read last is only stored.
Once you fix that, you might come across the second question. It's very common and I myself came across that issue long back. So I'm gonna answer that as well.
Let's say your file has 3 lines:
line1
line2
line3
Initially your file control (pointer) is at the beginning, exactly where line 1 starts. After iterations when it comes to line3, we know it's last line as we input the data. But the loop control doesn't know that. For all it knows, there could be a million more lines. Only after it enters the loop condition THE NEXT TIME will it come to know that the file has ended. So the final value will be printed twice.
I am using the code with ifstream that I used ~1 year ago, but now it does not work correctly. Here, I have the following file (so, just a line of integers):
2 4 2 3
I read it while constructing a graph from this file:
graph g = graph("file.txt");
where graph constructor starts with:
#include <iostream>
#include <fstream>
#include <sstream>
using namespace std;
graph::graph(const char *file_name) {
ifstream infile(file_name);
string line;
getline(infile, line);
cout << line << endl; // first output
istringstream iss;
iss.str(line);
iss >> R >> C >> P >> K;
iss.clear();
cout << R << " " << C << " " << P << " " << K; // second output
}
The second output (marked in code), instead of giving me 2 4 2 3, returns random(?) values -1003857504 32689 0 0. If I add the first output to check the contents of line after getline, it is just an empty string "".
All the files (main.cpp where a graph is instantiated, 'graph.cpp' where the graph is implemented and 'file.txt') are located in the same folder.
As I mentioned, this is my old code that worked before, so probably I do not see some obvious mistake which broke it. Thanks for any help.
These two locations:
where your program's original source code is located
where your program's input data is located
are completely unrelated.
Since "file.txt" is a relative path, your program looks for input data in the current working directory during execution. Sometimes that is the same as where the executable is. Sometimes it is not. (Only you can tell what it is, since it depends on how you execute your program.) There is never a connection to the location of the original source file, except possibly by chance.
When the two do not match, you get this problem, because you perform no I/O error checking in your program.
If you checked whether infile is open, I bet you'll find that it is not.
This is particularly evident since the program stopped working after a period of time without any changes to its logic; chances are, the only thing that could have changed is the location of various elements of your solution.
As you can see, I have a cout here before the loop starts. Seekg starts at the beginning and the first word in the txtfile is "Hello". But it doesn't print it out(the first cout).
When I remove the while loop, then its not a problem, the first word gets included in the output.
The first "cout", shouldn't it be printed out no matter what comes after it? How is it possible that next lines of code(THIS case) affects the previous "cout" above it ?
int main()
{
string a;
ifstream myfile;
myfile.open("test.txt");
myfile.seekg(0);
getline(myfile,a);
cout << a << endl;
int z = 0;
while( a != "x" ) {
myfile.seekg(z);
getline(myfile,a);
z += a.size() + 2;
cout << a << endl;
}
}
I Also should mention that the file starts with "hello", AND contains 600 newlines and a word on every new line. The last line contains "x".
[EDIT]
Here's another example. I belive this will be helpful. This is my code now:
int main() {
string a;
ifstream myfile;
int newpos = 0;
myfile.open("example.txt");
myfile.seekg(newpos);
getline(myfile,a);
while (a != "x") {
myfile.seekg(newpos);
getline(myfile,a);
cout << a << endl;
newpos += a.size() + 2;
}
}
This is my textfile:
hello
johan
nils
erik
john
x
The output is exactly as it looks in the textfile above.(so far so good).
BUT, then I add about 600 new names to the list/textfile(same structure as above, no changes there, just new names added). Only ONE "hello" at the top so I can track the start, and one x at the end.
This still works with around 100 new names, hello is still printed out in the beginning. But when i add around 600 new names , hello will not be included(the very first cout). Why is that?
But when I add around 600 new names, hello will not be included (the very first cout).Why is that?
Looks like your Screen Buffer Size wasn't big enough to show all of the buffer lines. So when the number of printed lines exceeds a specific height, the console starts to ignore the previously printed lines which result you think it didn't print them all.
Since you're using Windows you can try to increase it as so
For all console apps
Right-click the title of the console and choose Defaults
go to Layout tab
Under the Screen Buffer Size, Increase the Height to (i.e 9001)
Click OK then restart the console
For a specific app
Right-click the title of the console and choose Properties
go to Layout tab
Under the Screen Buffer Size, Increase the Height to (i.e 9001)
Click OK.
Note that the Default Height in most Windows Operating systems is 9001.
I am trying to create a new file with data from two different existing files. I need to copy the first existing file in it's entirety, which I have done successfully. For the second existing file I need to copy just the last two columns and append it to the first file at the end of each row.
Ex:
Info from first file already copied into my new file:
20424297 1092 CSCI 13500 B 3
20424297 1092 CSCI 13600 A- 3.7
Now I need to copy the last two columns of each line in this file and then append them to the appropriate row in the file above:
17 250 3.00 RNL
17 381 3.00 RLA
i.e. I need "3.00" and "RNL" appended to the end of the first row, "3.0" and "RLA" appended to the end of the second row, etc.
This is what I have so far:
#include <iostream>
#include <fstream>
#include <string>
#include <sstream>
#include <cstdlib>
using namespace std;
int main() {
//Creates new file and StudentData.tsv
ofstream myFile;
ifstream studentData;
ifstream hunterCourseData;
//StudentData.tsv is opened and checked to make sure it didn't fail
studentData.open("StudentData.tsv");
if(studentData.fail()){
cout << "Student data file failed to open" << endl;
exit(1);
}
//My new file is opened and checked to make sure it didn't fail
myFile.open("file.txt");
if(myFile.fail()){
cout << "MyFile file failed to open" << endl;
exit(1);
}
//HunterCourse file is opened and checked to make sure if didn't fail
hunterCourseData.open("HunterCourse.tsv");
if(myFile.fail()){
cout << "Hunter data file failed to open" << endl;
exit(1);
}
// Copies data from StudentData.tsv to myFile
char next = '\0';
int n = 1;
while(! studentData.eof()){
myFile << next;
if(next == '\n'){
n++;
myFile << n << ' ';
}
studentData.get(next);
}
return 0;
}
I am going bananas trying to figure this out. I'm sure it's a simple fix but I can't find anything online that works. I've looked into using ostream and a while loop to assign each row into a variable but I can't get that to work.
Another approach that has crossed my mind is just to remove all integers from the second file because I only need the last two columns and neither of those columns include integers.
If you take a look at the seekg method of a file-stream, you'll note the second version allows you to implement the location to set an offset from (such as ios_base::end which sets the offset compared to the end of the file. With this you can effectively read backwards from the end of the a file.
Consider the following
int Pos=0;
while(hunterCourseData.peek()!= '\n')
{
Pos--;
hunterCourseData.seekg(Pos, ios_base::end);
}
//this line will execute when you have found the first newline-character from the end of the file.
Much better code is available at this Very Similar question
Another possibility is simply to find how many lines are in the file beforehand. (less fast, but workable), in this case one would simply loop though the file calling getline and increment a count variable, reset to the start, then repeat until reaching the count - 2. Though I wouldn't use this technique myself.
i have a text file with data like the following:
name
weight
groupcode
name
weight
groupcode
name
weight
groupcode
now i want write the data of all persons into a output file till the maximum weight of 10000 kg is reached.
currently i have this:
void loadData(){
ifstream readFile( "inFile.txt" );
if( !readFile.is_open() )
{
cout << "Cannot open file" << endl;
}
else
{
cout << "Open file" << endl;
}
char row[30]; // max length of a value
while(readFile.getline (row, 50))
{
cout << row << endl;
// how can i store the data into a list and also calculating the total weight?
}
readFile.close();
}
i work with visual studio 2010 professional!
because i am a c++ beginner there could be is a better way! i am open for any idea's and suggestions
thanks in advance!
#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <limits>
struct entry
{
entry()
: weight()
{ }
std::string name;
int weight; // kg
std::string group_code;
};
// content of data.txt
// (without leading space)
//
// John
// 80
// Wrestler
//
// Joe
// 75
// Cowboy
int main()
{
std::ifstream stream("data.txt");
if (stream)
{
std::vector<entry> entries;
const int limit_total_weight = 10000; // kg
int total_weight = 0; // kg
entry current;
while (std::getline(stream, current.name) &&
stream >> current.weight &&
stream.ignore(std::numeric_limits<std::streamsize>::max(), '\n') && // skip the rest of the line containing the weight
std::getline(stream, current.group_code))
{
entries.push_back(current);
total_weight += current.weight;
if (total_weight > limit_total_weight)
{
break;
}
// ignore empty line
stream.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
}
}
else
{
std::cerr << "could not open the file" << std::endl;
}
}
Edit: Since you wannt to write the entries to a file, just stream out the entries instead of storing them in the vector. And of course you could overload the operator >> and operator << for the entry type.
Well here's a clue. Do you see the mismatch between your code and your problem description? In your problem description you have the data in groups of four lines, name, weight, groupcode, and a blank line. But in your code you only read one line each time round your loop, you should read four lines each time round your loop. So something like this
char name[30];
char weight[30];
char groupcode[30];
char blank[30];
while (readFile.getline (name, 30) &&
readFile.getline (weight, 30) &&
readFile.getline (groupcode, 30) &&
readFile.getline (blank, 30))
{
// now do something with name, weight and groupcode
}
Not perfect by a long way, but hopefully will get you started on the right track. Remember the structure of your code should match the structure of your problem description.
Have two file pointers, try reading input file and keep writing to o/p file. Meanwhile have a counter and keep incrementing with weight. When weight >= 10k, break the loop. By then you will have required data in o/p file.
Use this link for list of I/O APIs:
http://msdn.microsoft.com/en-us/library/aa364232(v=VS.85).aspx
If you want to struggle through things to build a working program on your own, read this. If you'd rather learn by example and study a strong example of C++ input/output, I'd definitely suggest poring over Simon's code.
First things first: You created a row buffer with 30 characters when you wrote, "char row[30];"
In the next line, you should change the readFile.getline(row, 50) call to readFile.getline(row, 30). Otherwise, it will try to read in 50 characters, and if someone has a name longer than 30, the memory past the buffer will become corrupted. So, that's a no-no. ;)
If you want to learn C++, I would strongly suggest that you use the standard library for I/O rather than the Microsoft-specific libraries that rplusg suggested. You're on the right track with ifstream and getline. If you want to learn pure C++, Simon has the right idea in his comment about switching out the character array for an std::string.
Anyway, john gave good advice about structuring your program around the problem description. As he said, you will want to read four lines with every iteration of the loop. When you read the weight line, you will want to find a way to get numerical output from it (if you're sticking with the character array, try http://www.cplusplus.com/reference/clibrary/cstdlib/atoi/, or try http://www.cplusplus.com/reference/clibrary/cstdlib/atof/ for non-whole numbers). Then you can add that to a running weight total. Each iteration, output data to a file as required, and once your weight total >= 10000, that's when you know to break out of the loop.
However, you might not want to use getline inside of your while condition at all: Since you have to use getline four times each loop iteration, you would either have to use something similar to Simon's code or store your results in four separate buffers if you did it that way (otherwise, you won't have time to read the weight and print out the line before the next line is read in!).
Instead, you can also structure the loop to be while(total <= 10000) or something similar. In that case, you can use four sets of if(readFile.getline(row, 30)) inside of the loop, and you'll be able to read in the weight and print things out in between each set. The loop will end automatically after the iteration that pushes the total weight over 10000...but you should also break out of it if you reach the end of the file, or you'll be stuck in a loop for all eternity. :p
Good luck!