Simple program to open up a file and read it's contents. Then a test at the end to see if I did in fact get the information. Every time I run it it tells me that it cannot open the file. I will post the contents of SaleSlips below. Why isn't it opening the file? It is also attempting to delete the file every run as well.
#include <iostream>
#include <fstream>
#include <cstdlib>
using namespace std;
struct SaleSlip{
char name[20];
int prodID;
double value;
};
void main(){
fstream slips;
SaleSlip sales[17];
slips.open("SaleSlips.txt", ios::in);
if(slips.eof()){
cout << "Cannot open file - SaleSlips.txt"<< endl;
system("pause");
exit(2);
}
int i = 0;
while(!slips.eof()){
slips.getline(sales[i].name, ' ');
slips >> sales[i].prodID;
slips.ignore(5, ' ');
slips >> sales[i].value;
slips.ignore(80, ' ');
i++;
}
cout << sales[1].value;
slips.close();
system("pause");
}
Eric 1 200000.00
Sookie 2 200.00
Sookie 4 200.50
You're opening the stream in output mode by using ios::out. Use ios::in to read from it.
You've got a lot of other issues, too. IE:
-The if(!slips.eof()) after the file open will always cause an exit unless the file is empty.
-In your while loop, you are (probably accidentally) attempting to write the prodID and value into the slips file using <<. Use >> to read from a stream and << to write to it.
You have two problems:
You're opening the file for output (writing)
slips.open("SaleSlips.txt", ios::out);
Useios::in instead for input (reading)
slips.open("SaleSlips.txt", ios::in);
Next, you're immediately testing for !eof(), which is the wrong logic.
if(!slips.eof())
You don't want to be at eof() when opening the file for input. eof() is end of file. When first opening the file for input you want to be at the beginning of the file; being at eof() is a bad thing. Your code should error out if eof() is true, not if it's false:
if(slips.eof()) {
// It's an error if we're starting at eof()
}
Related
I created a data file called program.txt. I need to create code that prints out number of lines and integer values from that program.txt
Heres the text I made
1
35
45
87
9
100
the program.text has these values in it
#include <iostream>
#include <string>
#include <fstream>
using namespace std;
int main()
{
string calc;
int test;
int cool;
int book;
ifstream myfile;
ifstream outof;
myfile.open ("program.txt");
outof.open("program.txt");
if (myfile.fail())
{
cerr<<"Error Opening file"<<endl;
}
if(outof.fail ())
{
cerr<<"Error Opening file"<<endl;
}
while (!myfile.eof ())
{
getline(myfile,calc);
++book;
}
cout <<book<<endl;
while (!outof.eof ())
{
outof<<test;//
cool++;
}
cout<<cool<<endl;
myfile.close();
outof.close();
}
Also after cerr I tried exit (1) and it said exit was not defined.
I am new to this any help would be greatly appreciated. Thanks This is C++ btw.
The problem is that you are using ifstream, which stands for INPUT file stream. You want to use ofstream, which is OUTPUT file stream. You cannot write to an input file stream, hence why the << operator is not defined.
Also, rather than using exit(1) after your errors, you can just return 1; as you are inside your main function. This will terminate the program, returning 1 as the exit code.
If you really want to use exit, you need to #include <cstdlib>.
Your defined input and expected output aren't clearly defined, so I'm not sure what you're trying to do. However, here's a general idea:
Putting the filename in a fstream's constructor will automatically try to open the file for read/write. You dont need to call .open() anymore. Also, you shouldnt be reading and writing to the same file simultaneously if you dont know what you're doing.
std::ifstream myInputFile("program.txt");
std::ofstream myOutputFile("programOut.txt");
Rather than checking myInputFile.fail(), just use the overloaded boolean operator. In depth explanation: ifstream::is_open vs ifstream::fail?
if (!myInputFile) {
//Something went wrong
std::cerr << "Failed to open input file" << std::endl;
return 1;
}
Define your std::string to hold lines as you read them, read all of your input file, and count the lines.
std::string line;
int lineCount = 0;
while (getline(myInputFile,line)) {
++lineCount;
//Do something with 'line'
}
Maybe you'll need to store the lines from your input file so that you can output the count of the lines at the beginning of your output file, you might want to #include <vector> and do something like this:
std::string line;
std::vector<std::string> linesFromFile;
//Read in all lines of the input file and store them in the vector
while (getline(myInputFile, line)) {
linesFromFile.emplace_back(line);
}
//All lines read, good time to close input file
myInputFile.close();
//Print number of lines read
myOutputFile << linesFromFile.size() << std::endl;
//Loop through lines and print them
for (auto &lineFromFile : linesFromFile) {
myOutputFile << lineFromFile << std::endl;
}
//Done outputting, close output file
myOutputFile.close();
#include <iostream>
#include <fstream>
#include <stdlib.h>
#include <process.h>
using namespace std;
int main(){
system("cls");
char mline[75];
int lc=0;
ofstream fout("out.txt",ios::out);
ifstream fin("data.txt",ios::in);
if(!fin){
cerr<<"Failed to open file !";
exit(1);
}
while(1){
fin.getline(mline,75,'.');
if(fin.eof()){break;}
lc++;
fout<<lc<<". "<<mline<<"\n";
}
fin.close();
fout.close();
cout<<"Output "<<lc<<" records"<<endl;
return 0;
}
The above code is supposed to read from the file "data.txt" the following text
"The default behaviour of ifstream type stream (upon opening files ) allows users
to read contents from the file. if the file mode is ios::in only then reading is
performed on a text file and if the file mode also includes ios::binary along with
ios::in then, reading is performed in binary mode. No transformation of characters
takes place in binary mode whereas specific transformations take place in text mode."
and create a file out.txt , in which the same text is stored using line numbers ( A line can have 75 characters or ends at '.' - whichever occurs earlier ).
Whenever I run the program, it just gets stuck at the console - which doesnt respond upon pressing any keys whatsoever.
Can someone tell me what's going on in here ?
If any one of the attempted reads in the file is longer than 74 characters, getline will set the failbit for fin, and you will never reach the end of the file. Change your code to the following:
for (; fin; ++lc) {
fin.getline(mline,75,'.');
if (!fin.eof() && !fin.bad())
fin.clear();
fout<<lc<<". "<<mline<<"\n";
}
This will break your loop if you reach the end of the file or if something catastrophic happens to the stream. You'll also need to think about handling the extra read that is performed if the file ends with a period.
Consider switching to std::string.
#include <iostream>
#include <fstream>
#include <string>
int main()
{
int lc = 0;
std::ofstream fout("out.txt");
std::ifstream fin("data.txt");
for (std::string line; getline(fin, line, '.'); )
fout << ++lc << ". " << line << "\n";
std::cout << "Output " << lc << " records\n";
}
So I am working on a program for class in which we have to open two different text files to retrieve the appropriate text to be displayed in the console. My code is not opening the file and keeps outputting the else statement ".txt file cannot be open". I've tried several different ways to open the file but with no luck. Any help here would be greatly appreciated.
//
// main.cpp
// PunchLine program
// Page 896 Problem 3
//
//
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main()
{
//File stream objects
fstream inFile;
string line;
//Open joke file to read lines to console
inFile.open("joke.txt", ios::in);
if (inFile.is_open())
{
//Read lines from file to console
while (getline(inFile, line))
{
cout << line << endl;
inFile.close();
}
}
else
cout << "joke.txt file cannot be open.\n";
//Open punchline file to read last line joke to console
inFile.open("punchline.txt", ios::in);
if (inFile.is_open())
{
//Read last line from file to console
inFile.seekp(-52L, ios::end);
getline(inFile, line);
}
else
cout << "punchline.txt file cannot be open.\n";
return 0;
}
When declaring an input file use
ifstream inFile;
Also make sure the input file is in the same folder as your .exe
Edit: http://www.cplusplus.com/doc/tutorial/files/ also, this link should help with working with files.
Edit 2: I already posted this in a comment, but I'll just add it to the official answer: "Change your while loop as well. Instead of the if test, use while(inFile.is_open()) and then use your getline statement inside the loop. Because right now your code reads like while get this line from the file is true cout line. So it might not even be doing the while loop."
I don't think you should close the file inside the while loop. Otherwise, your file gets closed after only the first line is read in. Move the close statement outside the loop. Same for the second block.
if (inFile.is_open())
{
//Read lines from file to console
while (getline(inFile, line))
{
cout << line << endl;
}
inFile.close();
}
else
cout << "joke.txt file cannot be open.\n";
Check that your file exist. If it does, check whether you have the correct path when you open it (check if your .txt files are in the same directory as your .exe file, or specify the full path in your code). If yes, check if the files are read-only.
use
if(!infile)
{
cout<<"cannot open file";
}
I think you need to flush the screen. Once you have flushed and closed the stream. The next time you run an application it should open the file.
e.g.
inFile.flush();
inFile.close();
When I debug this I can see it opens datafile1 , it reads the firstline and
in the logfile I get roma-3-4.log
It change to c:/temp/roma-3-4.log but when I want to open it , it fails. I have check that the _Mystate = 2 .
What is the meaning of that
Thanks
in the transfersubs.cfg there is this
roma-3-4.log
** In the directory c:/temp/ I have the following file
roma-3-4.log
#include <iostream>
#include <fstream>
#include <string>
#include <vector>
using namespace std;
int main()
{
string input;
string logfile;
string errorfile;
short logfilesize1;
fstream dataFile1("c:/temp/transfersubs.cfg", ios::in);
if (dataFile1)
{
getline(dataFile1, input, '$');
logfile=input;
logfilesize1=input.size();
errorfile=input;
errorfile[logfilesize1-4]='e';
errorfile[logfilesize1-3]='r';
errorfile[logfilesize1-2]='r';
logfile="C:/Temp/"+logfile;
fstream dataFile2( logfile, ios::in);
if (dataFile2)
{
dataFile2.close();
}
else
{
cout << "ERROR: Cannot open logfile.\n";
}
dataFile1.close();
}
else
{
cout << "ERROR: Cannot open file.\n";
}
system("Pause");
return 0;
}
I believe your getline doesn't bother looking the newline but only for a $. You didn't post the file you are reading from, but check to ensure it has a $ at the end of the file name otherwise it will fetch the entire file.
It appears that unless you put a \n or endl after writing to the file using ofstream, ifstream won't be able to read anything from the file. In fact, adding a space after whatever you've written into file won't help either.
So always add a newline right after whatever it is that you've written to file using ofstream.
Im working on a two part program that uses an encoder do encode a text file then a decoder to decode the text file. However i cannot get my decoder to read the whole text file it just reads the first line. How do i fix this, ive played around with the loops but it is not helping me.
#include <fstream>
#include <iostream>
#include <string>
using namespace std;
int main()
{
ifstream fin;
ofstream fout;
string lineFromFile;
fin.open("secret.txt");
if (!fin.good()) throw "I/O error";
fout.open("secret.txt", ios::app);
if (!fout.good()) throw "I/O error";
while (fin.good())
{
getline(fin, lineFromFile);
for (int i = 0; i < lineFromFile.length(); i++) // for each char in the string...
lineFromFile[i]--; // bump the ASCII code by 1
fout << lineFromFile << endl;
}//while
fin.close();
fout.close();
return 0;
}
You are closing the stream in the first iteration (i.e., after reading the first line). Then you open the output stream to write the first line. Only then do you reach the end of the while-loop, at which time fin.good() cannot be true anymore since you closed fin.
The loop should contain only the reading and writing. Opening done before the loop, closing done after.
Additional suggestion: Use proper indenting, it helps understanding the control flow.
I think the problem might be that you are reading and writing from the same file: secret.txt. I do not know what the expected behaviour is but when I ran the code it was infinite, which makes some sense as you are appending.
Try changing the ouput stream, fout, to a different file name.
The while loop that currently processes the file will process a final invalid read as you do not check if getline() was successful until the loop condition. I would suggest changing to:
for (;;)
{
getline(fin, lineFromFile);
if (!fin.good())
{
break;
}
for (int i = 0; i < lineFromFile.length(); i++)
lineFromFile[i]--;
fout << lineFromFile << endl;
}
Perhaps that because another file handle,fout, accesses the file to which fin is tied, fin is closed as a side-effect. Either that, or because fout appends to the file, the file pointer is pointed to the end of the file, and so because there is no more input to read, the loop ends.
(These are hypotheses; I am not familiar enough with the specifics of C++ I.O. to conclusively say what is happening.)
If you are supposed to replace the original file with an encoded version, I recommend setting the file tied to fout to a temporary file for the duration of your code above, closing both fin and fout, and then copying the file associated with fout over the file associated with fin.
Otherwise, just tie fout to a different filename than fin, such as "encoded.txt".