Tutorials

C Library – time.h

Posted in C Tutorial

Updated on Oct 06, 2024

By Mari Selvan

👁️ 401 - Views

⏳ 4 mins

💬 1 Comment

Photo Credit to CodeToFun

🙋 Introduction

The <time.h> header file in the C programming language provides functions and macros for manipulating date and time.

This library is essential for applications that require time-related functionalities, such as timestamping events, measuring intervals, and formatting dates and times.

💡 Syntax

To use the functions and macros provided by <time.h>, include the header file at the beginning of your C program:

example.c

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#include <time.h>

📚 Key Functions and Macros

Here are some of the key functions and macros available in <time.h>:

time():

Returns the current calendar time as a time_t object.
example.c
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```
time_t current_time;
current_time = time(NULL);
```
difftime():

Returns the difference in seconds between two time_t values.
example.c
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```
double difference;
difference = difftime(time1, time2);
```

clock():

Returns the processor time consumed by the program.

example.c

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clock_t start, end;
start = clock();
/* Some computation */
end = clock();
double cpu_time_used = ((double) (end - start)) / CLOCKS_PER_SEC;

gmtime():

Converts a time_t value to a tm structure representing Coordinated Universal Time (UTC).
example.c
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```
struct tm *utc_time;
time_t current_time = time(NULL);
utc_time = gmtime(¤t_time);
```

localtime():

Converts a time_t value to a tm structure representing local time.

example.c

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struct tm *local_time;
time_t current_time = time(NULL);
local_time = localtime(¤t_time);

strftime():

Formats a tm structure as a string.

example.c

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char buffer[80];
struct tm *time_info;
time_t rawtime = time(NULL);
time_info = localtime(&rawtime);
strftime(buffer, 80, "Now it's %I:%M%p.", time_info);

📝 Basic Example:

Here's a complete example demonstrating the use of several <time.h> functions to print the current date and time:

example.c

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#include <stdio.h>
#include <time.h>

int main() {
  time_t current_time;
  struct tm *local_time;
  char buffer[80];

  // Get the current time
  time(¤t_time);

  // Convert to local time format
  local_time = localtime(¤t_time);

  // Format time as a string
  strftime(buffer, 80, "Current date and time: %Y-%m-%d %H:%M:%S", local_time);
  printf("%s\n", buffer);

  return 0;
}

💻 Output

Output

Current date and time: 2024-06-02 10:51:02

💰 Benefits

Using the <time.h> library offers several benefits:

Standardization: As part of the C standard library, <time.h> provides a consistent and portable way to handle time-related functions across different platforms and compilers.
Ease of Use: The functions and macros in <time.h> are straightforward and easy to use, making it accessible even for beginners.
Comprehensive Functionality: With a wide range of functions, <time.h> covers various aspects of time manipulation, from simple time retrieval to complex formatting and interval calculations.
Performance: The library functions are optimized for performance, ensuring efficient time calculations and manipulations, which is crucial for time-sensitive applications.
Interoperability: The time_t and tm structures provide a standardized way to store and manipulate time data, facilitating interoperability with other libraries and systems that use similar time representations.

🎉 Conclusion

The <time.h> library in C is a powerful tool for handling various time-related operations. By leveraging the functions and macros it provides, you can perform complex time manipulations and formatting with ease.

Understanding and utilizing <time.h> is crucial for developing applications that depend on accurate and efficient time management.