getline并立即测试EOF

时间:2016-07-16 11:04:32

标签: c++ fstream eof getline

我想问一下我的问题,我试图阅读Getline和EOF问题,但没有帮助。

问题是我不知道在哪里可能出错: 使用过的功能(getline或检查EOF)有问题吗?

如果text.txt文件中没有文字,则表示发现了某些内容。但我不知道为什么或在哪里犯了错误......

我想要的是:搜索字符串,如果txt文件中没有文字我想要它说EOF或其他东西。它仍然说 - 即使文件是空的 - 我在寻找的字符串在第一行找到,第一位 - 例如

我在那里写代码:

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

using namespace std;

int openFile(void);
int closeFile(void);
int getTime(void);
int findTime();
int findDate();
int stringFind(string);
bool getOneLine(void);

string what;
bool ifound = false;
string foundstring;
string filename ;
fstream inputfile;
string sentence ;
size_t found ;
string foundTime ;
string foundDate ;
bool timeIsHere = false;
bool dateIsHere = false;

int iterTime = 0;
int iterDate = 0;
int line = 0;


int main (void){
    sentence.clear();

    cout << " Enter the file name:" << endl;

    openFile();


    while (getOneLine() != false) {
        stringFind("Time");
    }




    cout << "END OF PROGRAM" << endl;
    system("PAUSE");
    ///getTime();
    closeFile();


    system("PAUSE");
}


int closeFile(void) {
    inputfile.close();
    cout << " File: " << filename <<  " - was closed...";
    return 0;
}

int openFile(void) {

    cout << " Insert file name in program directory or full path to desired file you want to edit:"<<endl;
    cout << " Do not use path with a space in directory address or filename ! " << endl;
    cout<<" ";
    getline(cin, filename);

    inputfile.open(filename, ios::in);

    cout <<" file_state: " << inputfile.fail();
    if (inputfile.fail() == 1) {
        cout << " - Cannot open your file" << endl;
    }
    else cout << " - File was openned sucesfully"<< endl;



    return 0;

}


int stringFind(string what) {
    cout << " I am looking for:" << what << endl;

    found = what.find(sentence);
    if (found == string::npos) {
        cout << " I could not find this string " << endl;

    }
    else if(found != string::npos){
        cout << " substring was found in line: " << line + 1 << " position: " << found + 1 << endl << endl;
        ifound = true;
        foundstring = sentence;

    }

    return 0;


}  



bool getOneLine(void) {
    if (inputfile.eof()) {
        cout << "END OF FILE" << endl << endl;
        return false;
    }
    else{
        getline(inputfile, sentence);
        cout << "next sentence is: "<< sentence  << endl;
        return true;
        }
}

我是新手,我无人问 - 亲自。我试图编辑while循环和IF,以确保我没有犯严重的错误,但我不知道。

我尝试使用例如sample.txt,此文件为空。

3 个答案:

答案 0 :(得分:2)

使用getline()EOF检查的正确方法如下:

bool getOneLine(void) {
    if (getline(inputfile, sentence)) {
        cout << "next sentence is: "<< sentence  << endl;
        return true;
    }
    if (inputfile.eof())
        cout << "EOF reached" << endl;
    else
        cout << "Some IO error" << endl;
    return false;
}

答案 1 :(得分:2)

始终测试强读取后输入是否成功!流不知道你想要做什么。它只能报告尝试是否成功到目前为止。所以,你会做类似

的事情
if (std::getline(stream, line)) {
    // deal with the successful case
}
else {
    // deal with the failure case
}

在失败的情况下,可能想要使用use eof()来确定故障是否到达流的末尾:到达文件末尾,因此{设置{1}}通常不是错误,而只是表明你已经完成了。它可能仍然是一个错误,例如,当知道要读取多少行但获得的行数较少时。

答案 2 :(得分:0)

你有一个错误:

found = what.find(sentence);

您正在what内寻找sentence。如果sentence为空,则会找到它。

将其更改为

found = sentence.find(what);

您应该明确地学习如何使用调试器。这样你会很快发现这些问题!