note 95413 deleted from function.fread by cmb
| From: | cmb@php.net | Date: | Sun, 12 Jan 2020 08:21:41 +0000 |
| Subject: | note 95413 deleted from function.fread by cmb | ||
| References: | 1 | Groups: | php.notes |
| Request: | Send a blank email to php-notes+get-213851@lists.php.net to get a copy of this message | ||
Note Submitter: Tblue
----
Note that fread() returns an empty string if you try to read beyond EOF, while the manual states
otherwise ("Returns [...] FALSE on failure."). This e. g. happens with empty files (0
bytes long).
This does not look like a bug in PHP's fread() implementation to me, but rather like a
documentation bug. The manpage for the C function fread() states:
> fread() does not distinguish between end-of-file and error, and callers must use feof(3) and
> ferror(3) to determine which occurred.
It also says:
> If an error occurs, or the end-of-file is reached, the return value is a short item count (or
> zero).
That means that in the case of empty files, C's fread() returns 0 and thus we get an empty PHP
string: PHP's fread() does not seem to check for errors as the manpage recommends; that's
fine, the PHP programmer has to do it, but it would be nice if this behaviour would be explicitly
documented.
In short: When using fread(), you have to check for FALSE and empty strings. Consider the following
wrapper function:
<?php
function my_fread( $handle, $length )
{
if( ( $ret = fread( $handle, $length ) ) === '' )
{
return false;
}
return $ret;
}
?>