How Can I Convert String Time to time_t and Compare String Times in C ?

Converting String Time to Time_t in C

When working with time data in C , it's often necessary to convert between strings and the time_t type, which represents time as an integer number of seconds since the Unix epoch. This article explores two questions related to time conversion and comparison.

Converting a String Time

Suppose you have a string variable, time_details, containing time in the format "hh:mm:ss," such as "16:35:12." To convert this string to time_t, you can use the std::get_time function:

struct std::tm tm;
std::istringstream ss("16:35:12");
ss >> std::get_time(&tm, "%H:%M:%S");
std::time_t time = mktime(&tm);

Here, tm is a std::tm struct representing the dissected time components. std::istringstream is used to read the time string, and mktime converts the tm struct to time_t.

Comparing Two String Times

Comparing two strings containing time can be useful for determining the earliest time. For example, suppose you have two strings, curr_time and user_time, representing times as "18:35:21" and "22:45:31."

To compare these times, you can convert them to std::time_t types using the same technique as above. Once you have the time_t values, you can simply use the standard comparison operators (<, <=, >, >=) to determine the earliest time.

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