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Converting a String Representing Time to time_t in C
When working with time in C , you may encounter scenarios where you have a string that represents a specific time and need to convert it into the portable time_t data type. The time_t type represents time as the number of seconds elapsed since January 1, 1970, 00:00:00 UTC.
Conversion to time_t
In C 11 and later, the std::get_time function can be used to parse a string into a std::tm struct, which can then be converted to time_t using mktime:
#include <iostream> #include <sstream> #include <time.h> int main() { std::string time_details = "16:35:12"; std::tm tm; std::istringstream ss(time_details); ss >> std::get_time(&tm, "%H:%M:%S"); std::time_t time = mktime(&tm); // Print the converted time_t std::cout << "Converted time: " << time << std::endl; return 0; }
Comparing Two Times
Once you have multiple times in the time_t format, you can compare them to determine which is earlier.
#include <iostream> #include <time.h> int main() { std::string curr_time = "18:35:21"; // Current time std::string user_time = "22:45:31"; // User's time std::tm curr_tm, user_tm; std::istringstream ss; // Parse both times ss.str(curr_time); ss >> std::get_time(&curr_tm, "%H:%M:%S"); ss.clear(); ss.str(user_time); ss >> std::get_time(&user_tm, "%H:%M:%S"); // Compare the time_t values std::time_t curr_secs = mktime(&curr_tm); std::time_t user_secs = mktime(&user_tm); if (curr_secs < user_secs) { std::cout << "Current time is earlier than user's time" << std::endl; } else { std::cout << "User's time is earlier than current time" << std::endl; } return 0; }
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