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tempnam (PHP 3, PHP 4, PHP 5) tempnam -- Create file with unique file name Descriptionstring tempnam ( string dir, string prefix )
Creates a file with a unique filename in the specified directory.
If the directory does not exist, tempnam() may
generate a file in the system's temporary directory, and return
the name of that.
Prior to PHP 4.0.6, the behaviour of the
tempnam() function was system dependent. On
Windows the TMP environment variable will override the
dir parameter, on Linux the TMPDIR
environment variable has precedence, while SVR4 will always use
your dir parameter if the directory it
points to exists. Consult your system documentation on the
tempnam(3) function if in doubt.
Note:
If PHP cannot create a file in the specified dir
parameter, it falls back on the system default.
Returns the new temporary filename, or FALSE on
failure.
Example 1. tempnam() example |
<?php
$tmpfname = tempnam("/tmp", "FOO");
$handle = fopen($tmpfname, "w");
fwrite($handle, "writing to tempfile");
fclose($handle);
unlink($tmpfname);
?>
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Note:
This function's behavior changed in 4.0.3. The temporary file is also
created to avoid a race condition where the file might appear in the
filesystem between the time the string was generated and before
the script gets around to creating the file. Note, that you need
to remove the file in case you need it no more, it is not done
automatically.
See also tmpfile() and unlink().
User Contributed Notes
tempnam
php at REMOVEMEkennel17 dot co dot uk
06-Mar-2005 12:10
Note that tempnam returns the full path to the temporary file, not just the filename.
17-Feb-2005 08:13
Regarding Typo3 and Safe mode "Generally, everything in TYPO3 can work under safe_mode and open_basedir as long as the script permissions are correct. Notice, this is not something TYPO3 can do better or worse; for a working TYPO3 system there must be access to writing files and directories in the filesystem and this is done by plain PHP functions."
Sebastian Kun
21-Jan-2005 03:03
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).
Nick Smith
20-Jan-2005 01:35
It is worth noting that if the 'dir' that you supply doesn't exist, then it is silently ignored and the system /tmp directory used. At least under Linux, PHP v4.1.2.
I had a script that appeared to work fine with safe mode switched off, but I didn't realise that my 'dir' parameter had a typo (so the files were going in /tmp), and once safe mode was switched on I started getting errors because the rest of the script couldn't read files from the system /tmp folder.
soletan at toxa dot de
02-Dec-2004 10:45
tempnam and SAFE MODE don't generally exclude each other - that link below just shows frustrating trials to find some meaning in SAFE MODE. However, SAFE MODE is good and I'd appreciate to find it used in more of contemporarily hyped projects like typo3 or similar, since many people don't seem to care about security that much, but get enraged by tens and hundreds of Spam-Mails a day.
Okay, that post from Feb-2004 and the "bug report" is unconditionally true for multi-hosted PHP environments where several users may have their individual scripts placed on same server machine. Just take a visit to one of your local webspace-providers, that give space for 5 € or less a month.
But the truth get conditional if you gain access to the server all by yourself and may set it up to have your script's and the web server's GID being same so you can "fall back" to GID-based SAFE MODE and use tempnam as desired. This is true for several local work, intranet-related projects in your company etc. Just take a look at how SAFE MODE _really_ works and why it's rockingly important to use it. You should do when you're developing a company tool for public access at least.
Never forget to take a moment to think about Unix-filesystem and access rights as well ... even if you're locally running Windows to have some great IDE or similar (like me :). PHP is available on both systems, but that's not succeeding to define your work as "portable".
andi<at>splitbrain<dot>org
08-Aug-2004 09:28
tempname ignores the current umask and always creates the file with permission 0600.
anakin dot skyw at gmx dot de
04-Jul-2004 10:20
>Under UNIX (where you can rename onto an extant file and so I used link), you will have to remove both the link and the link's target.
Couldn't you do
<?php
if ($newFileCreated) {
unlink ($sysFileName);
return $newFileName;
}
?>
and get the same semantics as the windows version?
bishop
30-Apr-2004 10:03
Creating a temporary file with a specific extension is a common requirement on dynamic websites. Largely this need arises from Microsoft browsers that identify a downloaded file's mimetype based on the file's extension.
No single PHP function creates a temporary filename with a specific extension, and, as has been shown, there are race conditions involved unless you use the PHP atomic primitives.
I use only primitives below and exploit OS dependent behaviour to securely create a file with a specific postfix, prefix, and directory. Enjoy.
<?php
function secure_tmpname($postfix = '.tmp', $prefix = 'tmp', $dir = null) {
if (! (isset($postfix) && is_string($postfix))) {
return false;
}
if (! (isset($prefix) && is_string($prefix))) {
return false;
}
if (! isset($dir)) {
$dir = getcwd();
}
$tries = 1;
do {
$sysFileName = tempnam($dir, $prefix);
if ($sysFileName === false) {
return false;
}
$newFileName = $sysFileName . $postfix;
if ($sysFileName == $newFileName) {
return $sysFileName;
}
$newFileCreated = (isWindows() ? @rename($sysFileName, $newFileName) : @link($sysFileName, $newFileName));
if ($newFileCreated) {
return $newFileName;
}
unlink ($sysFileName);
$tries++;
} while ($tries <= 5);
return false;
}
?>
The isWindows function is mostly left as an exercise for the reader. A starting point is below:
<?php
function isWindows() {
return (DIRECTORY_SEPARATOR == '\\' ? true : false);
}
?>
Like tempnam(), this function requires you to cleanup your own files later. Under UNIX (where you can rename onto an extant file and so I used link), you will have to remove both the link and the link's target. Cleanup is left entirely to the reader.
kulpp at wsg dot net
03-Feb-2004 01:57
phpdoc at rickbradley dot com
25-Nov-2003 05:54
The "newtempnam" recipe provided below (posted by "tempnam" on " 23-Jul-2003 08:56") has at least one race condition. The while loop checks to make sure that the file in question doesn't exist, and then goes and creates the file. In between the existence test and the fopen() call there is an opportunity for an attacker to create the file in question.
This is a classic race-condition, and while it seems difficult to exploit there are a number of well-known attacks against this kind of sloppy file creation.
The atomic primitives necessary to implement secure file creation are not available at the language level in PHP. This further underscores the need for PHP-language developers to rely on the language's security primitives (including tempnam() and tempfile()) instead of rolling their own.
23-Jul-2003 12:56
The tempnam() function will not let you specify a postfix to the filename created. Here is a function that will create a new filename with pre and post fix'es. Not returns false if it can't create in the dir specified where tempnam() creates in the systems temp dir.
function newtempnam($dir, $prefix, $postfix){
/* Creates a new non-existant file with the specified post and pre fixes */
if ($dir[strlen($dir) - 1] == '/') {
$trailing_slash = "";
} else {
$trailing_slash = "/";
}
/*The PHP function is_dir returns true on files that have no extension.
The filetype function will tell you correctly what the file is */
if (!is_dir(realpath($dir)) || filetype(realpath($dir)) != "dir") {
// The specified dir is not actualy a dir
return false;
}
if (!is_writable($dir)){
// The directory will not let us create a file there
return false;
}
do{ $seed = substr(md5(microtime().posix_getpid()), 0, 8);
$filename = $dir . $trailing_slash . $prefix . $seed . $postfix;
} while (file_exists($filename));
$fp = fopen($filename, "w");
fclose($fp);
return $filename;
}
lreilly at lanl dot gov
28-Aug-2002 07:54
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
seb at nospam dot 50carleton dot com
22-May-2001 07:24
In addition to a note previously posted, on Windows NT Server 4.0, I noticed that tempnam() only uses the first THREE characters of the specified prefix.
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