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POParsing a YYYY-MM-DD date strictly on Linux
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copied!<p>POSIX defines a handy function, <code>strptime</code>, that can be used for parsing dates and times. Thus, theoretically, if I have a date of the format "YYYY-MM-DD", I should be able to use <code>strptime</code> to parse it like this:</p> <pre><code>char myDate[] = "2012-01-01"; struct tm result; char *end = strptime(myDate, "%Y-%m-%d", &result); </code></pre> <p>… and get it back out in its canonical representation with:</p> <pre><code>if (end != NULL) { char outDate[11]; strftime(outDate, sizeof(outDate), "%Y-%m-%d", &result); printf("%s\n", outDate); } else printf("Invalid date\n"); </code></pre> <p>On OS X and Linux, this prints out 2012-01-01. So far so good! However, let's say my input date is in the wrong format: 01-01-2012.</p> <p>If I run the above code again, on OS X, I get "Invalid date", which is expected. However, on Linux, I get 1-01-20 — January 20th, 1 (yes, year one).</p> <p>OS X follows the specifiers strictly, parsing a string as <code>%Y</code> <em>only</em> where a four-digit year exists. Linux takes a few liberties, though, and interprets two digits as a year — it doesn't even appear that it assumes it's 2001, it treats it as year 1!</p> <p>This can be worked around by changing my <code>if</code> statement to something like</p> <pre><code>if (end != NULL && *end == '\0') </code></pre> <p>… but that seems hokey. Does anyone know if it's possible to make <code>strptime</code> on Linux behave more strictly, and fail for <code>%Y</code> if the input string does not have a four-digit year?</p>

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