The C date and time functions are a group of functions in the standard library of the C programming language implementing date and time manipulation operations.[1] They provide support for time acquisition, conversion between date formats, and formatted output to strings.
The C date and time operations are defined in the time.hheader file (ctime header in C++).
Identifier
Description
Time manipulation
difftime
computes the difference in seconds between two time_t values
time
returns the current time of the system as a time_t value, number of seconds, (which is usually time since an epoch, typically the Unix epoch). The value of the epoch is operating system dependent; 1900 and 1970 are often used. See RFC 868.
converts a time_t value to calendar time expressed as local time
mktime
converts calendar time to a time_t value.
Constants
CLOCKS_PER_SEC
number of processor clock ticks per second
TIME_UTC
time base for UTC
Types
struct tm
broken-down calendar time type: year, month, day, hour, minute, second
time_t
arithmetic time type (typically time since the Unix epoch)
clock_t
process running time type
timespec
time with seconds and nanoseconds
The timespec and related types were originally proposed by Markus Kuhn to provide a variety of time bases, but only TIME_UTC was accepted.[3] The functionalities were, however, added to C++ in 2020 in std::chrono.
#include<time.h>#include<stdlib.h>#include<stdio.h>intmain(void){time_tcurrent_time;char*c_time_string;/* Obtain current time. */current_time=time(NULL);if(current_time==((time_t)-1)){(void)fprintf(stderr,"Failure to obtain the current time.\n");exit(EXIT_FAILURE);}/* Convert to local time format. */c_time_string=ctime(¤t_time);if(c_time_string==NULL){(void)fprintf(stderr,"Failure to convert the current time.\n");exit(EXIT_FAILURE);}/* Print to stdout. ctime() has already added a terminating newline character. */(void)printf("Current time is %s",c_time_string);exit(EXIT_SUCCESS);}
^ISO/IEC 9899:1999 specification(PDF). p. 351, § 7.32.2.
^open-std.org - Committee Draft -- May 6, 2005 page 355
^Markus Kuhn. "Modernized API for ISO C". cl.cam.ac.uk.
External links
The Wikibook C Programming has a page on the topic of: C Programming/C Reference
March 03, 2023
date, time, functions, this, article, written, like, manual, guidebook, please, help, rewrite, this, article, from, descriptive, neutral, point, view, remove, advice, instruction, october, 2014, learn, when, remove, this, template, message, group, functions, s. This article is written like a manual or guidebook Please help rewrite this article from a descriptive neutral point of view and remove advice or instruction October 2014 Learn how and when to remove this template message The C date and time functions are a group of functions in the standard library of the C programming language implementing date and time manipulation operations 1 They provide support for time acquisition conversion between date formats and formatted output to strings Contents 1 Overview of functions 2 Example 3 See also 4 References 5 External linksOverview of functions EditThe C date and time operations are defined in the time h header file ctime header in C Identifier DescriptionTimemanipulation difftime computes the difference in seconds between two time t valuestime returns the current time of the system as a time t value number of seconds which is usually time since an epoch typically the Unix epoch The value of the epoch is operating system dependent 1900 and 1970 are often used See RFC 868 clock returns a processor tick count associated with the processtimespec get C11 returns a calendar time based on a time baseFormatconversions asctime converts a struct tm object to a textual representation deprecated ctime converts a time t value to a textual representationstrftime converts a struct tm object to custom textual representationstrptime converts a string with time information to a struct tmwcsftime converts a struct tm object to custom wide string textual representationgmtime converts a time t value to calendar time expressed as Coordinated Universal Time 2 localtime converts a time t value to calendar time expressed as local timemktime converts calendar time to a time t value Constants CLOCKS PER SEC number of processor clock ticks per secondTIME UTC time base for UTCTypes struct tm broken down calendar time type year month day hour minute secondtime t arithmetic time type typically time since the Unix epoch clock t process running time typetimespec time with seconds and nanosecondsThe timespec and related types were originally proposed by Markus Kuhn to provide a variety of time bases but only TIME UTC was accepted 3 The functionalities were however added to C in 2020 in std chrono Example EditThe following C source code prints the current time to the standard output stream include lt time h gt include lt stdlib h gt include lt stdio h gt int main void time t current time char c time string Obtain current time current time time NULL if current time time t 1 void fprintf stderr Failure to obtain the current time n exit EXIT FAILURE Convert to local time format c time string ctime amp current time if c time string NULL void fprintf stderr Failure to convert the current time n exit EXIT FAILURE Print to stdout ctime has already added a terminating newline character void printf Current time is s c time string exit EXIT SUCCESS The output is Current time is Thu Sep 15 21 18 23 2016See also EditUnix time Year 2038 problemReferences Edit ISO IEC 9899 1999 specification PDF p 351 7 32 2 open std org Committee Draft May 6 2005 page 355 Markus Kuhn Modernized API for ISO C cl cam ac uk External links Edit The Wikibook C Programming has a page on the topic of C Programming C Reference Retrieved from https en wikipedia org w index php title C date and time functions amp oldid 1118266324, wikipedia, wiki, book, books, library,
