...
$select->execute();
$result = $select->fetchall();
// displays products on discount with an Html table style
echo '<p style="font-size: 20px; text-align: center;">Active discounts</p>
<div class="table">
<div class="thead">
<span class="th">Product</span>
<span class="th">Public price</span>
<span class="th">Discount price</span>
<span class="th">Discount code</span>
<span class="th">Description</span>
<span class="th">New code</span>
<span class="th"> </span>
<span class="th"> </span>
</div>';
foreach($result as $row) // loop on Products
{
$discount_price = $row['product_price'] - ($row['product_price'] * $row['discount_percent'] );
// wrap each "tr like' in a form
echo '<form class="tr" action="" method="post">
<span class="td">'.$row['product_name'].'</span>
<span class="td">'.$row['product_price'].'</span>
<span class="td">'.$discount_price.'</span>
<span class="td">'.$row['product_discount'].'</span>
<span class="td">'.$row['discount_desc'].'</span>';
// populate discount codes in drop-down
$select_d = $connexion -> prepare(
"SELECT
discount_code
FROM Discounts"
);
$select_d->execute();
$result_d = $select_d->fetchall();
// build select for each product
echo "<span class='td'><select id='discount' name='discount'>
<option value='' selected='selected'>-Select-</option>";
foreach($result_d as $row_d) { // loop on Discounts
echo "<option value='".$row_d['discount_code']."'>".$row_d['discount_code']."</option>";
}
// end select & action buttons
echo '</select></span>
<span class="td"><button class="btn btn-danger bold" type="submit" name="change" value="'.$row['productID'].'">Change</button></span>
<span class="td"><button class="btn btn-danger bold" type="submit" name="reset" value="'.$row['productID'].'">Reset</button></span>
</form>';
} // end loop Products
echo '</div><br />'; // end display html table style
$connexion = null;
...
是一个库调用，它首先将数据缓冲到用户空间缓冲区，然后稍后调用fwrite()系统调用以实际执行写操作。
如果程序调用{{1}}将某些数据写入文件但存在异常，则
write()的缓冲区将被清除刷新，否则缓冲的数据将是留在记忆中？
我正在考虑的操作系统是Linux。
答案 0 :(得分：8)
如果您的程序异常退出，则不会刷新任何缓冲的数据。操作系统只是说“哦，亲爱的，你把文件描述符打开了，我最好为你关闭”，当进程终止时;它不知道有一些随机数据存在于内存中，程序打算写入磁盘，但没有。