Question

我正在寻求有关如何使用C ++从txt文件中删除某些内容的帮助。我知道如何打开一个txt文件并写入它，但我不知道如何删除文件中的某些内容。例如，用户打开文件，并想在文件中写“apple”，之后他们在文件中添加“banana”，然后希望删除“apple”。

Answer 1

打开文件后，您可以继续一次读取其中的单词，然后一个简单的for循环应搜索该单词并将其删除，您可以使用char变量word[20]存储用户输入和另一个char array[]来存储文件内容。要运行循环，可以使用int变量target_length

for(int i = 0; array[i] != '\0'; i++)
{
    for(int j = 0; word[j] != '\0' && j < 20 ; j++)
    {
        if(array[i] != word[j])
        {
            break;
        }
        else
        {
            i++;
            if(word[j+1] == '\0')
            {
                for(int k = (i-target_length); array[k] != '\0'; k++)
                {
                    array[k] = array[k+target_length];
                }
                i = i - (target_length+1); // move the rest of the words one place left as words are deleted
            }
        }
    }
}

Answer 2

//My Assumption
//1.Comma use for seperation of string

#include <fstream> 
#include <string>
#include <vector>
void  main () 
{

    //Writing data in file (comma use as seperator)
    std::fstream fileStream;
    std::string fileName = "TEXT.txt";
    fileStream.open (fileName, std::fstream::in | std::fstream::out | std::fstream::app);
    fileStream << "APPLE"<<","<<"BANANA";
    fileStream.close();


    //Remove all "APPLE" from file
    std::ifstream readStream;
    std::string lineData;
    char * lineString;
    std::vector<char*> fileData; 

    readStream.open(fileName);
    if(readStream.is_open())
    {
        while(!readStream.eof())
        {
            std::getline (readStream,lineData);
            if(!lineData.empty())
            lineString = std::strtok(const_cast<char*>(lineData.c_str()),",");
            int i= 0;
            while (lineString!=nullptr)
            {
                if(strcmp(lineString,"APPLE")!=0)
                {
                    fileData.push_back(lineString);
                    fileData.push_back(",");
                }
                lineString = std::strtok(NULL, ",");

            }
        }
    }
    readStream.close();

    //Remove the original file
    remove(fileName.c_str());


    //Created a new file with same name
    fileStream.open(fileName, std::fstream::in|std::fstream::out|std::fstream::app);
    for(int i=0;i<fileData.size();i++)
    fileStream<< fileData[i];
    fileStream.close();

    fileData.clear();


}

1) I insert data in text file using fstream.
2) I searches "APPLE" string in file.
3) I copied all content of file in vector except "APPLE" String.
4) I Remove original file.
5) I created new file with same name copied all vector data in file.

使用C ++从文本文件中删除某些内容

2 个答案: