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| author | Craig Jennings <c@cjennings.net> | 2024-04-07 13:41:34 -0500 |
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| committer | Craig Jennings <c@cjennings.net> | 2024-04-07 13:41:34 -0500 |
| commit | 754bbf7a25a8dda49b5d08ef0d0443bbf5af0e36 (patch) | |
| tree | f1190704f78f04a2b0b4c977d20fe96a828377f1 /devdocs/c/chrono%2Fdifftime.html | |
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diff --git a/devdocs/c/chrono%2Fdifftime.html b/devdocs/c/chrono%2Fdifftime.html new file mode 100644 index 00000000..d72402bb --- /dev/null +++ b/devdocs/c/chrono%2Fdifftime.html @@ -0,0 +1,45 @@ + <h1 id="firstHeading" class="firstHeading">difftime</h1> <table class="t-dcl-begin"> <tr class="t-dsc-header"> <th> Defined in header <code><time.h></code> </th> <th> </th> <th> </th> </tr> <tr class="t-dcl"> <td class="t-dcl-nopad"> <pre data-language="c">double difftime( time_t time_end, time_t time_beg );</pre> +</td> <td class="t-dcl-nopad"> </td> <td class="t-dcl-nopad"> </td> </tr> </table> <p>Computes difference between two calendar times as <code><a href="time_t" title="c/chrono/time t">time_t</a></code> objects (<code>time_end - time_beg</code>) in seconds. If <code>time_end</code> refers to time point before <code>time_beg</code> then the result is negative.</p> +<h3 id="Parameters"> Parameters</h3> <table class="t-par-begin"> <tr class="t-par"> <td> time_beg, time_end </td> <td> - </td> <td> times to compare </td> +</tr> +</table> <h3 id="Return_value"> Return value</h3> <p>Difference between two times in seconds.</p> +<h3 id="Notes"> Notes</h3> <p>On POSIX systems, <code><a href="time_t" title="c/chrono/time t">time_t</a></code> is measured in seconds, and <code>difftime</code> is equivalent to arithmetic subtraction, but C and C++ allow fractional units for <code><a href="time_t" title="c/chrono/time t">time_t</a></code>.</p> +<h3 id="Example"> Example</h3> <div class="t-example"> +<p>The following program computes the number of seconds that have passed since the beginning of the month.</p> +<div class="c source-c"><pre data-language="c">#include <stdio.h> +#include <time.h> + +int main(void) +{ + time_t now = time(0); + + struct tm beg = *localtime(&now); + + // set beg to the beginning of the month + beg.tm_hour = 0, + beg.tm_min = 0, + beg.tm_sec = 0, + beg.tm_mday = 1; + + double seconds = difftime(now, mktime(&beg)); + + printf("%.f seconds have passed since the beginning of the month.\n", seconds); + + return 0; +}</pre></div> <p>Output:</p> +<div class="text source-text"><pre data-language="c">1937968 seconds have passed since the beginning of the month.</pre></div> </div> <h3 id="References"> References</h3> <ul> +<li> C17 standard (ISO/IEC 9899:2018): </li> +<ul><li> 7.27.2.2 The difftime function (p: 285) </li></ul> +<li> C11 standard (ISO/IEC 9899:2011): </li> +<ul><li> 7.27.2.2 The difftime function (p: 390) </li></ul> +<li> C99 standard (ISO/IEC 9899:1999): </li> +<ul><li> 7.23.2.2 The difftime function (p: 338) </li></ul> +<li> C89/C90 standard (ISO/IEC 9899:1990): </li> +<ul><li> 7.12.2.2 The difftime function (p: 171) </li></ul> +</ul> <h3 id="See_also"> See also</h3> <table class="t-dsc-begin"> <tr class="t-dsc"> <td colspan="2"> <span><a href="https://en.cppreference.com/w/cpp/chrono/c/difftime" title="cpp/chrono/c/difftime">C++ documentation</a></span> for <code>difftime</code> </td> +</tr> </table> <div class="_attribution"> + <p class="_attribution-p"> + © cppreference.com<br>Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.<br> + <a href="https://en.cppreference.com/w/c/chrono/difftime" class="_attribution-link">https://en.cppreference.com/w/c/chrono/difftime</a> + </p> +</div> |