Find a specific word inside file and delete its line [closed] - c++

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As the title suggests I am trying to find a specific word inside a file, and then deleting the line including it, but what I do here destroys the content of the file:
cin>>ID; //id of the line we want to delete
ifstream read;
read.open("infos.txt");
ofstream write;
write.open("infos.txt");
while (read >> name >> surname >> id) {
if (ID != id) {
write << name << " " << surname << " " << id << endl;
}
else write << " ";
}
read.close();
write.close();

Answer 1

Both of your files have same name. Calling basic_ofstream::open destroys content of a file if it already exists. In your case you destroyed data in input file before doing anything. Use different name and later rename. I assume line in input is ended with "\n" so we can use getline(). Then we need to tell if word is present in line and for that there is this function. std::string:npos is returned if line doesn't contain word.
#include <cstdio> // include for std::rename
#include <fstream>
#include <string>
void removeID() {
std::string ID;
cin >> ID; //id of the line we want to delete
ifstream read("infos.txt");
ofstream write("tmp.txt");
if (read.is_open()) {
std::string line;
while (getline(read, line)) {
if (line.find(ID) != std::string::npos)
write << line;
}
} else {
std::cerr << "Error: coudn't open file\n";
/* additional handle */
}
read.close();
write.close();
std::remove("infos.txt");
std::rename("tmp.txt", "infos.txt");
}