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

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< cpp‎ | chrono‎ | c
m (fmt, headers sorted)
 
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{{cpp/title| asctime}}
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{{cpp/title|ctime}}
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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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char *ctime( const time_t *time );
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char* ctime( const std::time_t* time );
 
}}
 
}}
  
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Converts given calendar time object {{tt|time}} to a human-readable time format.  
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Converts given time since epoch to a calendar local time and then to a textual representation, as if by calling {{c|std::asctime(std::localtime(time))}}. The resulting string has the following format:
  
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The resulting string has the following format:
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{{source|Www Mmm dd hh:mm:ss yyyy\n}}
  
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{{source|Www Mmm dd hh:mm:ss yyyy}}
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* {{tt|Www}} - the day of the week (one of {{tt|Mon}}, {{tt|Tue}}, {{tt|Wed}}, {{tt|Thu}}, {{tt|Fri}}, {{tt|Sat}}, {{tt|Sun}}).
 +
* {{tt|Mmm}} - the month (one of {{tt|Jan}}, {{tt|Feb}}, {{tt|Mar}}, {{tt|Apr}}, {{tt|May}}, {{tt|Jun}}, {{tt|Jul}}, {{tt|Aug}}, {{tt|Sep}}, {{tt|Oct}}, {{tt|Nov}}, {{tt|Dec}}).
 +
* {{tt|dd}} - the day of the month.
 +
* {{tt|hh}} - hours.
 +
* {{tt|mm}} - minutes.
 +
* {{tt|ss}} - seconds.
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* {{tt|yyyy}} - years.
  
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*{{tt|Www}} - the day of the week (one of {{tt|Mon}}, {{tt|Tue}}, {{tt|Wed}}, {{tt|Thu}}, {{tt|Fri}}, {{tt|Sat}}, {{tt|Sun}}).
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The function does not support localization.
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*{{tt|Mmm}} - the month (one of {{tt|Jan}}, {{tt|Feb}}, {{tt|Mar}}, {{tt|Apr}}, {{tt|May}}, {{tt|Jun}}, {{tt|Jul}}, {{tt|Aug}}, {{tt|Sep}}, {{tt|Oct}}, {{tt|Nov}}, {{tt|Dec}}).
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*{{tt|dd}} - the day of the month
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*{{tt|hh}} - hours
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*{{tt|mm}} - minutes
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*{{tt|ss}} - seconds
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*{{tt|yyyy}} - years
+
  
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<!-- ======== -->
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===Parameters===
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{{params}}
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{{par begin}}
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{{param list begin}}
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{{par|time|pointer to a {{lc|std::time_t}} object specifying the time to print}}
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{{param list item | time | pointer to a {{rlpt|time_t}} object specifying the time to print}}
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{{par end}}
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{{param list end}}
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<!-- ======== -->
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===Return value===
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{{returns}}
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Pointer to a static null-terminated character string holding the textual representation of date and time. The string may be shared between {{lc|std::asctime}} and {{tt|std::ctime}}, and may be overwritten on each invocation of any of those functions.
  
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pointer to a static character string. The string is shared among {{rlpf|ctime}} and {{rlpf|asctime}} and is overwritten on each invocation.
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===Notes===
 +
This function returns a pointer to static data and is not thread-safe. In addition, it modifies the static {{lc|std::tm}} object which may be shared with {{lc|std::gmtime}} and {{lc|std::localtime}}. POSIX marks this function obsolete and recommends {{lc|std::strftime}} instead.
  
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<!-- ======== -->
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The behavior may be undefined for the values of {{lc|std::time_t}} that result in the string longer than 25 characters (e.g. year 10000).
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{{example}}
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{{example cpp
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===Example===
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|
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{{example
−
  | code=
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|code=
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| output=
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#include <cassert>
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#include <cstring>
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#include <ctime>
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#include <iostream>
 +
   
 +
int main()
 +
{
 +
    std::time_t result = std::time(nullptr);
 +
    std::cout << std::ctime(&result);
 +
 
 +
    char buffer[32];
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    std::strncpy(buffer, std::ctime(&result), 26);
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    assert('\n' == buffer[std::strlen(buffer) - 1]);
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    std::cout << buffer;
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}
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|p=true
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|output=
 +
Mon Oct 11 17:10:55 2021
 +
Mon Oct 11 17:10:55 2021
 
}}
 
}}
  
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<!-- ======== -->
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===See also===
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{{see also}}
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{{dsc begin}}
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{{dcl list begin}}
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{{dsc inc|cpp/chrono/c/dsc asctime}}
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{{dcl list template | cpp/chrono/c/dcl list asctime}}
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{{dsc inc|cpp/chrono/c/dsc strftime}}
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{{dcl list end}}
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{{dsc inc|cpp/io/manip/dsc put_time}}
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{{dsc see c|c/chrono/ctime}}
 +
{{dsc end}}
 +
 
 +
{{langlinks|de|es|fr|it|ja|pt|ru|zh}}

Latest revision as of 22:19, 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
ctime
Constants
Types
(C++17)
 
Defined in header <ctime>
char* ctime( const std::time_t* time );

Converts given time since epoch to a calendar local time and then to a textual representation, as if by calling std::asctime(std::localtime(time)). The resulting string has the following format: 

Www Mmm dd hh:mm:ss yyyy\n
  • Www - the day of the week (one of Mon, Tue, Wed, Thu, Fri, Sat, Sun).
  • Mmm - the month (one of Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec).
  • dd - the day of the month.
  • hh - hours.
  • mm - minutes.
  • ss - seconds.
  • yyyy - years.

The function does not support localization.

Contents

[edit] Parameters

time - pointer to a std::time_t object specifying the time to print

[edit] Return value

Pointer to a static null-terminated character string holding the textual representation of date and time. The string may be shared between std::asctime and std::ctime, and may be overwritten on each invocation of any of those functions.

[edit] Notes

This function returns a pointer to static data and is not thread-safe. In addition, it modifies the static std::tm object which may be shared with std::gmtime and std::localtime. POSIX marks this function obsolete and recommends std::strftime instead.

The behavior may be undefined for the values of std::time_t that result in the string longer than 25 characters (e.g. year 10000).

[edit] Example

Run this code
#include <cassert>
#include <cstring>
#include <ctime>
#include <iostream>
 
int main()
{
    std::time_t result = std::time(nullptr);
    std::cout << std::ctime(&result);
 
    char buffer[32];
    std::strncpy(buffer, std::ctime(&result), 26);
    assert('\n' == buffer[std::strlen(buffer) - 1]);
    std::cout << buffer;
}

Possible output: 

Mon Oct 11 17:10:55 2021
Mon Oct 11 17:10:55 2021

[edit] See also

 converts a std::tm object to a textual representation
(function) [edit]
converts a std::tm object to custom textual representation
(function) [edit]
(C++11)
 formats and outputs a date/time value according to the specified format
(function template) [edit]
C documentation for ctime
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