tempnam()

(PHP 4, PHP 5, PHP 7)

建立一个具有唯一文件名的文件

说明

在指定目录中建立一个具有唯一文件名的文件。如果该目录不存在，tempnam()会在系统临时目录中生成一个文件，并返回其文件名。

参数

The directory where the temporary filename will be created.

产生临时文件的前缀。

Note:Windows uses only the first three characters of prefix.

返回值

返回新的临时文件名，出错返回FALSE。

更新日志

范例

Example #1tempnam()例子

注释

Note:如果 PHP 不能在指定的$dir参数中创建文件，则退回到系统默认值。在 NTFS 文件系统中，同样的情况也发生在$dir中文件数超过 65534 个的时候。

参见

• tmpfile() 建立一个临时文件
• sys_get_temp_dir() 返回用于临时文件的目录
• unlink() 删除文件

Watch out using a blank $dir as a "trick" to create temporary files in the system temporary directory.

If an open_basedir restriction is in effect, the trick will not work. You will get a warning message like
Warning: tempnam() [function.tempnam]: open_basedir restriction in effect.
File() is not within the allowed path(s): (/var/www/vhosts/example.com/httpdocs:/tmp)
What works is this: 

Please note that this function might throw a notice in PHP 7.1.0 and above. This was a bugfix: https://bugs.php.net/bug.php?id=69489
You can place an address operator (@) to sillence the notice:

Or you could try to set the "upload_tmp_dir" setting in your php.ini to the temporary folder path of your system. Not sure, if the last one prevents the notices.

Be careful with you forward and back slashes. Innocent looking code like this...
$uploaddir = "C:/Program Files/Apache Group/Apache2/htdocs/sasdap/uploads/";
$tempFile = tempnam ($uploaddir, "TMPANAL");
$fp = fopen($tmpfname, "w");
fwrite($fp, $iqdata);
//fclose($fp);
... may show something odd when echoing $tempFile";
i.e. /Program Files/Apache Group/Apache2/htdocs/sasdap/uploads/\TMP3D.tmp
                            
Must... remember... to... use... backslashes...
 - Lee P. Reilly

Note that tempnam returns the full path to the temporary file, not just the filename.

tempnam() function does not support custom stream wrappers registered by stream_register_wrapper(). 
For example if you'll try to use tempnam() on Windows platform, PHP will try to generate unique filename in %TMP% folder (usually: C:\WINDOWS\Temp) without any warning or notice.

ouputs:
--------------------
PHP 5.2.13
node exists: 1
node is writable: 1
node is dir: 1
tempnam in dir: C:\Windows\Temp\tmp1D03.tmp
If you want to create temporary file, you have to create your own function (which will probably use opendir() and fopen($filename, "x") functions)

If you go to the linux man page for the C function tempnam(3), you will see at the end "Never use this function. Use mkstemp(3) instead." But php's tempnam() function doesn't actually use tmpnam(3), so there's no problem (under Linux, it will use mkstemp(3) if it's available).

Notice that tempnam will return NULL (not false) if the second parameter  isn't transferred:

also the warning will be generated:
Warning: tempnam() expects exactly 2 parameters, 1 given in php shell code ...

Beware that on Windows NT and other windows, if you have, for example, a variable $work_dir with a path to some dir on your document root(or any other dir). Note the following: 

Creating a temporary file with a specific extension is a common requirement on dynamic websites. Largely this need arises from Microsoft browsers that identify a downloaded file's mimetype based on the file's extension.
No single PHP function creates a temporary filename with a specific extension, and, as has been shown, there are race conditions involved unless you use the PHP atomic primitives.
I use only primitives below and exploit OS dependent behaviour to securely create a file with a specific postfix, prefix, and directory. Enjoy.

The isWindows function is mostly left as an exercise for the reader. A starting point is below:

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