I have a JSP to upload a file which works fine. After the file has been uploaded I am trying to open the file again using the file path saved from the form data.
However, the filepath variable shows fine but the ifstream fails. If the csvFileName variable is set manually to path + file name it works fine. Doing this on a MAC and trying to avoid using boost library.
form_iterator two = cgi.getElement("csvFileName");
csvFileName=two->getValue();
form_iterator three = cgi.getElement("csvFilePath");
filePath = three->getValue();
csvFileName.c_str();
ifstream thefile;
thefile.open(csvFileName);
cout << "Filename is: " << csvFileName << endl;
if (thefile.is_open())
{
cout << "<H1>It's working</H1>" << endl;
while ( getline (thefile,line) )
{
cout << line << '\n';
}
thefile.close();
}
else
{
cout << strerror(errno) << endl;
}
Related
I am currently trying to read in a text file for use in a project but when running in release form (running the .exe file from a command window) the file doesn't read in. But yet in debug mode it works fine. I have tried having the files in the same directory as the .exe file but it doesn't seem to find it and I don't know why?
The code:
std::cout << "Acquiring data file..." << endl;
std::cout << "Reading data file..." << endl;
ifstream tempData;
tempData.open("temp_lincolnshire_short.txt");
if (tempData.is_open()) {
std::cout << tempData.rdbuf() << endl;
}
else {
cout << "Reading failed..." << endl;
}
tempData.close();
std::cout << "Data file closed." << endl;
What I ended up using was a relative path as identified on https://stackoverflow.com/a/35910234/3795116 which ended up being:
myFile.open("../Release/frequency.dat", ios::in);
*changing myFile to whatever your variable is.
I am trying to open a json file that I will be working with in C++. Code that I have used successfully before fails to open the file. I am using Visual Studio 2017 on Windows 10 Pro with JSON for Modern C++ version 3.5.0.
I have a very simple function, which is supposed to open a file as input to a json object. It appears to open the file, but aborts when writing it to the json object. Originally the file to be opened was in another directory, but I moved it into the same directory as the executable while testing...but it didn't help.
Here is the very short function that fails:
json baselineOpenAndRead(string fileName) //passed string used for filename
{
json baseJObject;
cout << "we have a baseJObject" << endl;
//ifstream inFileJSON("test_file.json"); // Making this explicit made no difference
ifstream inFileJSON;
inFileJSON.open("test_file.json", ifstream::in);
cout << "we have opened json inFileJSON" << endl; // get here
inFileJSON >> baseJObject;
cout << " Can direct inFileJSON into baseJObject" << endl; //never get here; the app aborts.
inFileJSON.close();
return baseJObject;
}
This seems basically identical to the example on the nlohmann site:
// read a JSON file
std::ifstream i("file.json");
json j;
i >> j;
I just expected this to open the json file, load it into the object, and return the object. Instead, it just quits.
Thanks for any thoughts...i.e., what am I doing wrong? (I'm going to ignore that it worked before...maybe I missed something).
--Al
As requested, here is a minimal reproducible example, but it will require nlohmann's json.hpp in order to compile:
#include <iostream>
#include <fstream>
#include "json.hpp"
using json = nlohmann::json;
using namespace std;
string fileName;
json baselineOpenAndRead(string);
int main(int argC, char *argV[])
{
json baseJObject;
if (argC != 2) // check to make sure proper number of arguments are given.
{
cout << "\n\nFilename needed...";
exit(1); // number of arguments is wrong - exit program
}
else
{
fileName = argV[1];
baseJObject = baselineOpenAndRead(fileName); // opens and reads the Base Line JSON file
cout << "baseJObject returned" << endl;
}
return 0;
}
json baselineOpenAndRead(string fileName) //
{
cout << "File name: " << fileName << endl;
json baseJObject;
cout << "we have a baseJObject" << endl;
ifstream inFileJSON(fileName);
if (inFileJSON.is_open())
{
cout << "file open..." << endl;
if (nlohmann::json::accept(inFileJSON))
{
cout << "valid json" << endl;
try { inFileJSON >> baseJObject; }
catch (const std::exception &e) { std::cout << e.what() << '\n'; throw; }
}
else
{
cout << "not valid json" << endl;
}
}
else
{
cout << "file not really open" << endl;
}
inFileJSON >> baseJObject;
cout << " We can echo inFileJSON into baseJObject" << endl;
inFileJSON.close();
return baseJObject;
}
I tested it with this json file:
{
"people": [{
"name": "Scott",
"website": "stackabuse.com",
"from": "Nebraska"
},
{
"name": "Larry",
"website": "google.com",
"from": "Michigan"
},
{
"name": "Tim",
"website": "apple.com",
"from": "Alabama"
}
]
}
When I run this passing it the json above as data.json, I get the following output and then it quits:
./Test_json data.json
File name: data.json
we have a baseJObject
file open...
valid json
[json.exception.parse_error.101] parse error at line 1, column 1: syntax error while parsing value - unexpected end of input; expected '[', '{', or a literal
Without the try, it just quits. It never gets past inFileJSON >> baseJObject;
Another try that seems to work, but why?
OK. I tried this with the same main (the only changes are in the function):
json baselineOpenAndRead(string fileName) //
{
json baseJObject;
string filePath = "../baselines/" + fileName;
cout << "filePath: " << filePath << endl;
ifstream inFileJSON(fileName);
//baseJObject = json::parse(inFileJSON);
inFileJSON >> baseJObject;
cout << baseJObject << std::endl;
return baseJObject;
}
This looks basically the same to me. I tried making it ifstream inFileJSON(fileName.c_str()) on both the original and in this one. The original continued to fail, this one continued to work. Sorry this is getting so long, but I can't get decent formatting out of comments... Should I just try answering my own question instead?
I think I've got this. I believe my initial problem was caused by an errant ',' in one of my json test files. Subsequently, the if (inFileJSON.is_open) worked, but the if (nlohmann::json::accept(inFileJSON) was failing and causing the same (or perhaps a similar) error. I thought that I needed the c_str() for file paths outside of the executable's directory, but it doesn't seem to make a difference one way or the other. I took out the accept(), and this code seems to work consistently:
json baselineOpenAndRead(string fileName) //
{
json baseJObject;
cout << "we have a baseJObject" << endl;
string filePath = "../baselines/" + fileName;
cout << "filePath: " << filePath << endl;
//ifstream inFileJSON(filePath.c_str());
ifstream inFileJSON(filePath);
if (inFileJSON.is_open())
{
cout << "File is open." << endl;
inFileJSON >> baseJObject;
cout << baseJObject << std::endl;
inFileJSON.close();
return baseJObject;
}
else
{
cout << "File not open." << endl;
exit(1);
}
}
Thanks to everyone for your help. I appreciate it.
--Al
IN IOS app, module written in C++ I am writing my data (map of basic strings and integers) to a text file. Using following method:
bool Recognizer::saveMap(const char * s)
{
if(trainingData.model && !trainingData.model.empty()) {
const string filename = string(s);
std::ofstream file(s, ios_base::trunc );
try{
if(! file.is_open())
{
file.open(s);
}
for (map<String,int>::iterator it=trainingData.idMap.begin(); it!=trainingData.idMap.end(); ++it)
{
cout << it->second << " " << it->first << endl;
file << it->first << endl << it->second << endl;
}
file.close();
}
catch(cv::Exception & e){
if(file.is_open())
file.close();
int code = e.code;
string message = e.err;
cerr << "cv::Exeption code: " << code << " " << message << endl;
return false;
}
std::streampos fileLength = iosFileSize(s);
cout << "Saved map to: " << filename << " length: " << fileLength << endl;
return true;
}
return false;
}
My contains one entry and console output indicates that two lines: string, string representing number have been written to my file.
Subsequent opening file for reading and reading using getline or using stream operator indicates that file is empty:
bool Recognizer::loadMap(const char * s)
{
std::streampos fileLenght = iosFileSize(s);
std::ifstream file(s, ios::in);
try{
if(file.is_open())
{
string name;
string lineName;
string lineTag;
int tag;
int count = 0;
while(getline(file,name))
{
if(getline(file,lineTag))
{
tag = stoi(lineTag,0,10);
count++;
cout << tag << " " << name << endl;
trainingData.idMap[name]=tag;
trainingData.namesMap[tag]=name;
}
}trainingData.personsCount=count;
file.close();
}
}
catch(cv::Exception & e){
if(file.is_open())
file.close();
int code = e.code;
string message = e.err;
cerr << "cv::Exeption code: " << code << " " << message << endl;
return false;
}
cout << "Loaded map from: " << s << " lenght: "<< fileLenght << endl;
return true;
}
I also copied from one of stackoverflow answers method returning file lenght and using it to verify lenghth of the file after write operation:
std::streampos iosFileSize( const char* filePath ){
std::streampos fsize = 0;
std::ifstream file( filePath, std::ios::binary );
fsize = file.tellg();
file.seekg( 0, std::ios::end );
fsize = file.tellg() - fsize;
file.close();
return fsize;
}
The file path passed to saveMap and loadMap seems to be legit. With path that the app could not write to, attempt to write caused exception.
There are no errors returned by write operation but both, attempts to read and iosFileSize() indicate that file is empty.
I am not sure if i need call file.open() and file.close() or file is open and closed automatically when output stream is created and later goes out of scope.
I experimented with those with the same result ( call to file.is_open returns true so the block calling file.open() is skipped.
What am I doing wrong?
I appreciate all responses.
It does not seem like you call file.flush(); anywhere in Recognizer::saveMap() after writing to the file stream. std::ofstream::flush() saves changes you've made to the file. Add file.flush(); between when you make changes to the code and when you close the file. See if that remedies your issue.
I also had the same issue. Using file.flush() everytime after you insert to a file can save your file.
However if you insert something like this, say,
file << "Insert This"; You will need to add file.flush().
But some people have issues, like if you just insert file << "Insert This" << endl; , this works fine. The key point here is that, std::endl calls flush() everytime it is used internally. you can say it is a shortend form of "\n" + flush().
I believe from looking at your code that you are overwriting your data when you open the file in the second program you should be using something like this.
std::fstream fs;
fs.open ("test.txt", ios::app)
instead of doing the ios::in
I am trying to run the following program:
#include <iostream>
#include <fstream>
using namespace std;
int main()
{
ifstream inFile;
ofstream outFile;
double first=1.49, second=2.59, third=3.69, fourth=4.79;
inFile.open("prices.txt");
char response;
if(!inFile.fail())
{
cout << "A file by the name prices.txt exists.\n" << "Do you want to continue and overwrite it\n" << " with the new data (y or n);"; cin >> response;
if(tolower(response) == 'n')
{
cout << "The existing file will not be overwritten." << endl;
return -1;
}
}
outFile.open("prices.txt");
if (inFile.fail())
{
cout << "\n The file does not exist and can not be opened" << endl;
cout << "The file has been successfully opened for output." << endl;
outFile << first << "\n" << second << "\n" << fourth << "\n" << endl;
outFile.close();
exit(1);
cout << "The file has been successfully opened for output. " << endl;
outFile << first << "\n" << second << "\n" << third << "\n" << fourth << endl;
outFile.close();
return 0;
}
}
Yet this program will not write the values to the prices.txt file. If you run the program once it says the file does not exist. Running it a second time says the file is already there and if you want to overwrite it. The thing is searching my Mac I cannot find this file anywhere.
Any ideas what I am doing wrong with running it in Xcode? A friend runs the exact same code in Visual Studio 2008 and it works. Any help is appreciated.
You need to set the working directory for the executable since you are assuming that your data files are in the current working directory. In Xcode 3.x you set this in the first tab of Get Info for the executable. In Xcode 4.x it has been moved, but the principle is the same.
Alternatively you can change your data file paths (e.g. make them absolute) so that you do not make assumptions about the current working directory.
You may not have permission to write into the directory that you are trying to save the file too.
Also, there is an error in your program and I am sure if it is there for debugging reasons. You have
outFile.close();
exit(1);
But then shortly there after you try to write to the file, then close it again.
I have a C++ program that reads a config file and gets the directories.
What I want to do now is to execute an .exe program using the directory settings from the config file.
Here is a piece of my code:
int main(){
ConfigFile cfg("htbaseconfig.properties");
bool exists = cfg.keyExists("backuplocation");
exists = cfg.keyExists("logdir");
exists = cfg.keyExists("execdir");
exists = cfg.keyExists("fulldir");
exists = cfg.keyExists("incdir");
exists = cfg.keyExists("appdir");
std::string bkploc = cfg.getValueOfKey<std::string>("backuplocation");
std::cout << "Backup Location: " << bkploc << "\n";
std::string bkplogdir = cfg.getValueOfKey<std::string>("logdir");
std::cout << "Log Location: " << bkplogdir << "\n";
std::string bkpexec = cfg.getValueOfKey<std::string>("execdir");
std::cout << "Exec Directory: " << bkpexec << "\n";
std::string bkpfulldir = cfg.getValueOfKey<std::string>("fulldir");
std::cout << "Full Directory: " << bkpfulldir << "\n";
std::string bkpappdir = cfg.getValueOfKey<std::string>("appdir");
std::cout << "Real app Directory: " << bkpappdir << "\n\n\n";
for( ; ; ) {
Sleep(6000);
ShellExecute(NULL, L"open", , L"C:\\teste.htm", NULL,SW_SHOWNORMAL);
}
std::cin.get();
return (0);}
Inside the ShellExecute, I wanted to execute the following line parsing the config options:
$execdir/program.exe $logdir/log.txt $bkpappdir $bkploc
How do I do this? I want to execute my program with the variables I get on std::cout.
You must pass to ShellExecute, instead of the second NULL, a string (c string, a char[]) that contains all parameters, like if you are passing them to the command line.
So Will be something like
ShellExecute(NULL, L"open", , L"C:\\teste.htm", "option=param option2=param2",SW_SHOWNORMAL);
Depends on how you parse them (or how they are parsed) from the other exe file