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Difference between revisions of "cpp/chrono/c/gmtime"

From cppreference.com
< cpp‎ | chrono‎ | c
m (Text replace - "{{example cpp" to "{{example")
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{{cpp/title| gmtime}}
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{{cpp/title|gmtime}}
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{{cpp/chrono/c/sidebar}}
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{{cpp/chrono/c/navbar}}
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{{ddcl | header=ctime |
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{{ddcl|header=ctime|
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std::tm* gmtime( const time_t* time );
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std::tm* gmtime( const std::time_t* time );
 
}}
 
}}
  
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Converts given time since epoch as {{cpp|std::time_t}} value into calendar time, expressed in Coordinated Universal Time (UTC).  
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Converts given time since epoch as {{lc|std::time_t}} value into calendar time, expressed in Coordinated Universal Time (UTC).  
  
 
===Parameters===
 
===Parameters===
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{{param list begin}}
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{{par begin}}
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{{param list item | time | pointer to a time_t object to convert}}
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{{par|time|pointer to a time_t object to convert}}
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{{param list end}}
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{{par end}}
  
 
===Return value===
 
===Return value===
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Pointer to a static internal {{lc|std::tm}} object on success, or null pointer otherwise. The structure may be shared between {{lc|std::gmtime}}, {{lc|std::localtime}}, and {{lc|std::ctime}} and may be overwritten on each invocation.
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pointer to a static internal {{cpp|std::tm}} object on success, or {{cpp|NULL}} otherwise. The structure may shared between {{cpp|std::gmtime}}, {{cpp|std::localtime}}, and {{cpp|std::ctime}} and may be overwritten on each invocation.
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===Notes===
 
===Notes===
 
This function may not be thread-safe.
 
This function may not be thread-safe.
  
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POSIX requires that this function sets {{cpp|errno}} to {{cpp|EOVERFLOW}} if it fails because the argument is too large.
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POSIX requires that this function sets {{lc|errno}} to {{lc|EOVERFLOW}} if it fails because the argument is too large.
  
 
===Example===
 
===Example===
 
{{example
 
{{example
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|
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|code=
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| code=
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#include <iostream>
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−
#include <iomanip>
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#include <ctime>
 
#include <ctime>
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#include <iomanip>
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#include <iostream>
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#include <sstream>
 +
 
int main()
 
int main()
 
{
 
{
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     std::time_t t = std::time(NULL);
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    setenv("TZ", "/usr/share/zoneinfo/Europe/London", 1); // POSIX-specific
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     std::cout << "UTC:  " << std::put_time(std::gmtime(&t), "%c %Z") << '\n'
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              << "local: " << std::put_time(std::localtime(&t), "%c %Z") << '\n';
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    std::tm tm{}; // get_time does not set all fields hence {}
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    tm.tm_year = 2020 - 1900; // 2020
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    tm.tm_mon = 7 - 1; // July
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    tm.tm_mday = 15; // 15th
 +
    tm.tm_hour = 10;
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    tm.tm_min = 15;
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    tm.tm_isdst = 1; // Daylight saving in London
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     std::time_t t = std::mktime(&tm);  
 +
 +
     std::cout << "UTC:  " << std::put_time(std::gmtime(&t), "%c %Z") << '\n';
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    std::cout << "local: " << std::put_time(std::localtime(&t), "%c %Z") << '\n';
 
}
 
}
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| output=
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|p=true
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UTC:  Wed Dec 28 11:44:28 2011 GMT
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|output=
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local: Wed Dec 28 06:44:28 2011 EST
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UTC:  Wed Jul 15 09:15:00 2020 GMT
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local: Wed Jul 15 10:15:00 2020 BST
 
}}
 
}}
  
 
===See also===
 
===See also===
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{{dcl list begin}}
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{{dsc begin}}
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{{dcl list template | cpp/chrono/c/dcl list localtime}}
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{{dsc inc|cpp/chrono/c/dsc localtime}}
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{{dcl list end}}
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{{dsc see c|c/chrono/gmtime}}
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{{dsc end}}
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 +
{{langlinks|de|es|fr|it|ja|pt|ru|zh}}

Latest revision as of 22:29, 19 August 2023

 
C++
 
Utilities library
General utilities
Relational operators (deprecated in C++20)
 
Date and time utilities
Time point
(C++11)
(C++20)
Duration
(C++11)
Clocks
(C++11)
(C++11)
(C++20)
(C++20)
(C++20)
(C++20)
Time of day
(C++20)(C++20)
(C++20)(C++20)
(C++20)

Calendar
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)(C++20)
Time zone
(C++20)
(C++20)
(C++20)(C++20)(C++20)(C++20)  
(C++20)
chrono I/O
(C++20)
C-style date and time
 
C-style date and time utilities
Functions
Time manipulation
(C++17)
Format conversions
gmtime
Constants
Types
(C++17)
 
Defined in header <ctime>
std::tm* gmtime( const std::time_t* time );

Converts given time since epoch as std::time_t value into calendar time, expressed in Coordinated Universal Time (UTC).

Contents

[edit] Parameters

time - pointer to a time_t object to convert

[edit] Return value

Pointer to a static internal std::tm object on success, or null pointer otherwise. The structure may be shared between std::gmtime, std::localtime, and std::ctime and may be overwritten on each invocation.

[edit] Notes

This function may not be thread-safe.

POSIX requires that this function sets errno to EOVERFLOW if it fails because the argument is too large.

[edit] Example

Run this code
#include <ctime>
#include <iomanip>
#include <iostream>
#include <sstream>
 
int main()
{
    setenv("TZ", "/usr/share/zoneinfo/Europe/London", 1); // POSIX-specific
 
    std::tm tm{}; // get_time does not set all fields hence {}
    tm.tm_year = 2020 - 1900; // 2020
    tm.tm_mon = 7 - 1; // July
    tm.tm_mday = 15; // 15th
    tm.tm_hour = 10;
    tm.tm_min = 15;
    tm.tm_isdst = 1; // Daylight saving in London
    std::time_t t = std::mktime(&tm); 
 
    std::cout << "UTC:   " << std::put_time(std::gmtime(&t), "%c %Z") << '\n';
    std::cout << "local: " << std::put_time(std::localtime(&t), "%c %Z") << '\n';
}

Possible output: 

UTC:   Wed Jul 15 09:15:00 2020 GMT
local: Wed Jul 15 10:15:00 2020 BST

[edit] See also

 converts time since epoch to calendar time expressed as local time
(function) [edit]
C documentation for gmtime
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