ltrim
I need to parse a big file after it was changed (a shared XLS file). I've fond a good idea to check once a minute the checksum of the file, in order to track if it was changed or not. Here is my code, hope will help some one. Any improvements are welcome!
<?php
$file_xls = "test.xls";
$file_md5 = "test.xls.md5"; // Must exists and must be writable for PHP
$md5_new_file = trim(md5_file($file_xls));
$md5_old_file = trim(file_get_contents($file_md5));
if($md5_new_file <> $md5_old_file)
{
echo "file is out of date, updating now...";
rename($file_md5, $file_md5.".bak");
$fp = fopen($file_md5, 'w');
fwrite($fp, $md5_new_file);
fclose($fp);
/*
Here we do some job...
In my case - dealing with "Spreadsheet Excel Reader"
*/
unlink($file_md5.".bak");
}
// "Not for crontab" - Remove the following section if you are intending to run it in crontab
else
{
echo "file is up to date, nothing to do...";
}
// End "Not for crontab";
?>
md5_file
(PHP 4 >= 4.2.0, PHP 5, PECL hash:1.1-1.3)
md5_file — Calculates the md5 hash of a given file
說明
string md5_file
( string $filename
[, bool $raw_output
] )
Calculates the MD5 hash of the file specified by the filename parameter using the » RSA Data Security, Inc. MD5 Message-Digest Algorithm, and returns that hash. The hash is a 32-character hexadecimal number.
參數
- filename
-
The filename
- raw_output
-
When TRUE, returns the digest in raw binary format with a length of 16. Defaults to FALSE.
Return值
Returns a string on success, FALSE otherwise.
更新日誌
| 版本 | 說明 |
|---|---|
| 5.0.0 | Added the raw_output parameter |
| 5.1.0 | Changed the function to use the streams API. It means that you can use it with wrappers, like md5_file('http://example.com/..') |
add a note
User Contributed Notesmd5_file
Sebastian Zavadschi (php.box.md)
22-Sep-2008 04:55
22-Sep-2008 04:55
smartin
12-Mar-2008 08:58
12-Mar-2008 08:58
In response to using exec instead for performance (Nov 13 2007 post), It looks like the performance depends on the size of the file. See the results below using the same script from the original post. The first hash is with md5_file and the second is with openssl md5.
With a 1MB file:
Hash = df1555ec0c2d7fcad3a03770f9aa238a; time = 0.005006
Hash = df1555ec0c2d7fcad3a03770f9aa238a; time = 0.01498
With a 2MB file:
Hash = 4387904830a4245a8ab767e5937d722c; time = 0.010393
Hash = 4387904830a4245a8ab767e5937d722c; time = 0.016691
With a 10MB file:
Hash = b89f948e98f3a113dc13fdbd3bdb17ef; time = 0.241907
Hash = b89f948e98f3a113dc13fdbd3bdb17ef; time = 0.037597
Performance seems to change proportionally with the file size. Judging from the previous post's default file name (.mov) he/she was probably dealing with a large file. These are just quick tests and far from a perfect benchmark, but you might want to test your own files before assuming that the openssl solution is faster (ie, if working with small text files vs. movies, etc)
toby at globaloptima dot co dot uk
19-Nov-2007 04:15
19-Nov-2007 04:15
I'm wondering about the MD5_DIR function posted by potsed, what happens if the file listing is returned in a different order?
From what I can tell you get different MD5's based on the order, a minor addition sorts this:
...
asort($filemd5s); //sort the md5s before concat
return md5(implode('', $filemd5s));
}
glau dot stuff at N0_SPAM dot ridiculousprods dot com
14-Nov-2007 09:54
14-Nov-2007 09:54
It's much faster to call an 'exec' command to openssl md5 than to use md5_file.
<?php
$file_path = '/path/to/large/video_file.mov';
$begin = microtime(true);
$hash = md5_file($file_path);
$end = microtime(true) - $begin;
echo "Hash = $hash; time = $end<br>";
# Hash = eac425a6f5b90f69e74710b015228640; time = 2.5333859920502
$begin = microtime(true);
$result = split('=',exec("openssl md5 $file_path"));
$end = microtime(true) - $begin;
echo "Hash = ".$result[1]."; time = $end";
#Hash = eac425a6f5b90f69e74710b015228640; time = 0.79528999328613
?>
I consistently see about a 3x improvement in speed.
potsed [at] gmail [dot] com
27-May-2007 07:12
27-May-2007 07:12
Heres a function to give an md5 for an entire directory..
function MD5_DIR($dir)
{
if (!is_dir($dir))
{
return false;
}
$filemd5s = array();
$d = dir($dir);
while (false !== ($entry = $d->read()))
{
if ($entry != '.' && $entry != '..')
{
if (is_dir($dir.'/'.$entry))
{
$filemd5s[] = MD5_DIR($dir.'/'.$entry);
}
else
{
$filemd5s[] = md5_file($dir.'/'.$entry);
}
}
}
$d->close();
return md5(implode('', $filemd5s));
}
bubba at revbubba dot com
29-Mar-2005 08:56
29-Mar-2005 08:56
a working example of the usage of this function, to confirm a specific file has not been modified (replace all instances of "myfile.xxx" with your filename):
<?php
$chkfilename = "myfile.xxx";
$chkmd5return = md5_file($chkfilename);
if ($chkmd5return != "myfile.xxx's md5 value") {
echo "You have replaced myfile.xxx with an unknown version of the file, please replace the original file.";
} else {
(your code to be executed, now that it has confirmed your myfile.xxx has been unmodified)
}
?>
To find out the file's md5 value, create a new .php doc, and put this code in it:
<?php
$chkfilename = "myfile.xxx";
$chkmd5return = md5_file($chkfilename);
echo $chkmd5return;
?>
Then upload the new .php doc to your webserver and navigate to it. Be sure to delete the new .php doc once you have plugged in the value it spits out, into the "myfile.xxx's md5 value" in the first example above.
I just thought this example might be helpful to someone somewhere... if you php.net people feel it needs editing or deletion, I leave it to your discretion. ;)
richard at interlink dot com dot au
16-Nov-2004 04:57
16-Nov-2004 04:57
For those of you with PHP 4 that want to output the "raw" 128 bit hash, all you need to do is send it to pack to convert the hex string into the raw output.
ie:
$filename="checkthisfile.bin";
$rawhash=pack("H*",md5_file($filename));