Programming Forums > Web Development and Design > PHP

grimpirate · May 24th, 2008, 5:07 PM

I'd like to know why I'm getting the following error:

Quote:

0

Warning: fread() [function.fread]: Length parameter must be greater than 0 in C:\Program Files\Apache Software Foundation\Apache2.2\htdocs\blah.php on line 22

with this code:

 PHP Syntax (Toggle Plain Text) 
<pre>
<?php
$filename = 'foo.txt';
 
$h1 = fopen($filename, 'xb');
fwrite($h1, 'bar');
//$h2 = fopen($filename, 'rb');
//echo fread($h2, filesize($filename));
//fclose($h2);
echo file_retrieve_contents($filename);
fclose($h1);
unlink($filename);
 
function file_retrieve_contents($filename, $offset = 0, $bytes = null){
	$fileSize = filesize($filename);
	echo $fileSize;
	if(!is_int($offset)) $offset = 0;
	if(!is_int($bytes)) $bytes = $fileSize - $offset;
 
	$handle = @fopen($filename, "rb");
	fseek($handle, $offset);
	$data = fread($handle, $bytes);
	fclose($handle);
	return $data;
}
?>
</pre>
<pre>
<?php
$filename = 'foo.txt';

$h1 = fopen($filename, 'xb');
fwrite($h1, 'bar');
//$h2 = fopen($filename, 'rb');
//echo fread($h2, filesize($filename));
//fclose($h2);
echo file_retrieve_contents($filename);
fclose($h1);
unlink($filename);

function file_retrieve_contents($filename, $offset = 0, $bytes = null){
	$fileSize = filesize($filename);
	echo $fileSize;
	if(!is_int($offset)) $offset = 0;
	if(!is_int($bytes)) $bytes = $fileSize - $offset;

	$handle = @fopen($filename, "rb");
	fseek($handle, $offset);
	$data = fread($handle, $bytes);
	fclose($handle);
	return $data;
}
?>
</pre>

And actually getting the output:

Quote:

bar

when I do the following:

 PHP Syntax (Toggle Plain Text) 
<pre>
<?php
$filename = 'foo.txt';
 
$h1 = fopen($filename, 'xb');
fwrite($h1, 'bar');
$h2 = fopen($filename, 'rb');
echo fread($h2, filesize($filename));
fclose($h2);
//echo file_retrieve_contents($filename);
fclose($h1);
unlink($filename);
 
function file_retrieve_contents($filename, $offset = 0, $bytes = null){
	$fileSize = filesize($filename);
	echo $fileSize;
	if(!is_int($offset)) $offset = 0;
	if(!is_int($bytes)) $bytes = $fileSize - $offset;
 
	$handle = @fopen($filename, "rb");
	fseek($handle, $offset);
	$data = fread($handle, $bytes);
	fclose($handle);
	return $data;
}
?>
</pre>
<pre>
<?php
$filename = 'foo.txt';

$h1 = fopen($filename, 'xb');
fwrite($h1, 'bar');
$h2 = fopen($filename, 'rb');
echo fread($h2, filesize($filename));
fclose($h2);
//echo file_retrieve_contents($filename);
fclose($h1);
unlink($filename);

function file_retrieve_contents($filename, $offset = 0, $bytes = null){
	$fileSize = filesize($filename);
	echo $fileSize;
	if(!is_int($offset)) $offset = 0;
	if(!is_int($bytes)) $bytes = $fileSize - $offset;

	$handle = @fopen($filename, "rb");
	fseek($handle, $offset);
	$data = fread($handle, $bytes);
	fclose($handle);
	return $data;
}
?>
</pre>

Anyone have any ideas?

Apophis · May 24th, 2008, 8:52 PM

With the second code you tell it to do a write to the file

(Toggle Plain Text)

 fwrite($h1, 'bar');

which will then give it the string 'bar'.
If you are trying to get it to add more text in to the file try:

(Toggle Plain Text)

$h1=fopen($filename, 'a');

grimpirate · May 24th, 2008, 10:12 PM

I'm not attempting to add more. I'm attempting to read that which has already been written.

Apophis · May 25th, 2008, 2:25 AM

then your code should be:

 php Syntax (Toggle Plain Text) 
<pre>
<?php
 
$filename = 'foo.txt';
$h2 = fopen($filename, 'rb');
echo fread($h2, filesize($filename));
fclose($h2);
//echo file_retrieve_contents($filename);
fclose($h1);
unlink($filename);
 
function file_retrieve_contents($filename, $offset = 0, $bytes = null){
$fileSize = filesize($filename);
echo $fileSize;
if(!is_int($offset)) $offset = 0;
if(!is_int($bytes)) $bytes = $fileSize - $offset;
$handle = @fopen($filename, "rb");
fseek($handle, $offset);
$data = fread($handle, $bytes);
fclose($handle);
return $data;
}
 
?></pre>
<pre>
<?php

$filename = 'foo.txt';
$h2 = fopen($filename, 'rb');
echo fread($h2, filesize($filename));
fclose($h2);
//echo file_retrieve_contents($filename);
fclose($h1);
unlink($filename);

function file_retrieve_contents($filename, $offset = 0, $bytes = null){
$fileSize = filesize($filename);
echo $fileSize;
if(!is_int($offset)) $offset = 0;
if(!is_int($bytes)) $bytes = $fileSize - $offset;
$handle = @fopen($filename, "rb");
fseek($handle, $offset);
$data = fread($handle, $bytes);
fclose($handle);
return $data;
}

?></pre>

The Dark · May 25th, 2008, 6:44 AM

In the first one your are getting the file size before you open the file again, in the second you open the file for reading before you get the file size. I suspect there that the write isn't being flushed to disk until a different IO is performed, so the file's size on disk doesn't match what you think it does.

May 24th, 2008, 8:52 PM	#2
Apophis Newbie Join Date: Apr 2008 Posts: 16 Rep Power: 0	Re: Strange fopen Problem With the second code you tell it to do a write to the file (Toggle Plain Text) fwrite($h1, 'bar'); fwrite($h1, 'bar'); which will then give it the string 'bar'. If you are trying to get it to add more text in to the file try: (Toggle Plain Text) $h1=fopen($filename, 'a'); $h1=fopen($filename, 'a');

May 24th, 2008, 10:12 PM	#3
grimpirate King of Portal Join Date: Sep 2005 Posts: 419 Rep Power: 3	Re: Strange fopen Problem I'm not attempting to add more. I'm attempting to read that which has already been written. __________________ Lo, there do I see my father. 'Lo, there do I see My mother, and my sisters, and my brothers. 'Lo, there do I see The line of my people... Back to the beginning. 'Lo, they do call to me. They bid me take my place among them. In the halls of Valhalla... Where the brave... May live... ...forever.. GrimBB \| Mimesis

May 25th, 2008, 2:25 AM	#4
Apophis Newbie Join Date: Apr 2008 Posts: 16 Rep Power: 0	Re: Strange fopen Problem then your code should be: php Syntax (Toggle Plain Text) <pre> <?php $filename = 'foo.txt'; $h2 = fopen($filename, 'rb'); echo fread($h2, filesize($filename)); fclose($h2); //echo file_retrieve_contents($filename); fclose($h1); unlink($filename); function file_retrieve_contents($filename, $offset = 0, $bytes = null){ $fileSize = filesize($filename); echo $fileSize; if(!is_int($offset)) $offset = 0; if(!is_int($bytes)) $bytes = $fileSize - $offset; $handle = @fopen($filename, "rb"); fseek($handle, $offset); $data = fread($handle, $bytes); fclose($handle); return $data; } ?></pre> <pre> <?php $filename = 'foo.txt'; $h2 = fopen($filename, 'rb'); echo fread($h2, filesize($filename)); fclose($h2); //echo file_retrieve_contents($filename); fclose($h1); unlink($filename); function file_retrieve_contents($filename, $offset = 0, $bytes = null){ $fileSize = filesize($filename); echo $fileSize; if(!is_int($offset)) $offset = 0; if(!is_int($bytes)) $bytes = $fileSize - $offset; $handle = @fopen($filename, "rb"); fseek($handle, $offset); $data = fread($handle, $bytes); fclose($handle); return $data; } ?></pre>

May 25th, 2008, 6:44 AM	#5
The Dark Expert Programmer Join Date: Jun 2005 Posts: 824 Rep Power: 4	Re: Strange fopen Problem In the first one your are getting the file size before you open the file again, in the second you open the file for reading before you get the file size. I suspect there that the write isn't being flushed to disk until a different IO is performed, so the file's size on disk doesn't match what you think it does.

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Programming Forums > Web Development and Design > PHP

Strange fopen Problem