How to Perform Partial String Replacement in C ?

Partial String Replacement in C

Replacing specific sections of a string is a common task in programming. This article explores how to perform such replacements using the standard C libraries.

Initially proposed using the Qt framework, which provides a specific replace method, we delve into the standard library approach.

Standard Library Solution

The standard library offers the find and replace functions separately. By combining these functions, we can implement a replacement mechanism:

bool replace(std::string& str, const std::string& from, const std::string& to) {
    size_t start_pos = str.find(from);
    if(start_pos == std::string::npos)
        return false;
    str.replace(start_pos, from.length(), to);
    return true;
}

int main() {
    std::string string("hello $name");
    replace(string, "$name", "Somename");
    return 0;
}

Replacing All Occurrences

To replace all occurrences of a substring, we can use a loop to iterate through the string and perform replacements accordingly:

void replaceAll(std::string& str, const std::string& from, const std::string& to) {
    if(from.empty())
        return;
    size_t start_pos = 0;
    while((start_pos = str.find(from, start_pos)) != std::string::npos) {
        str.replace(start_pos, from.length(), to);
        start_pos += to.length(); // In case 'to' contains 'from', like replacing 'x' with 'yx'
    }
}

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