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Top Forums UNIX for Dummies Questions & Answers Difference between file descriptor and file pointer Post 302403704 by DoxieLvr on Sunday 14th of March 2010 01:10:09 AM
Old 03-14-2010
Quote:
Originally Posted by jlliagre
While I would mostly agree with the file descriptor definition, a file pointer is not usually what you describe but commonly used to refer to what the standard C library uses to handle files (FILE *).

The associated functions are fopen, fclose, fread, fwrite, fscanf and the likes.
I would also note that a file pointer has an associated file descriptor used by the library functions to do the actual I/O calls to the kernel. You can get the associated fd using the fileno function.
 

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FREAD(3)								 1								  FREAD(3)

fread - Binary-safe file read

SYNOPSIS
string fread (resource $handle, int $length) DESCRIPTION
fread(3) reads up to $length bytes from the file pointer referenced by $handle. Reading stops as soon as one of the following conditions is met: o$length bytes have been read o EOF (end of file) is reached o a packet becomes available or the socket timeout occurs (for network streams) o if the stream is read buffered and it does not represent a plain file, at most one read of up to a number of bytes equal to the chunk size (usually 8192) is made; depending on the previously buffered data, the size of the returned data may be larger than the chunk size. PARAMETERS
o $handle -A file system pointer resource that is typically created using fopen(3). o $length - Up to $length number of bytes read. RETURN VALUES
Returns the read string or FALSE on failure. EXAMPLES
Example #1 A simple fread(3) example <?php // get contents of a file into a string $filename = "/usr/local/something.txt"; $handle = fopen($filename, "r"); $contents = fread($handle, filesize($filename)); fclose($handle); ?> Example #2 Binary fread(3) example Warning On systems which differentiate between binary and text files (i.e. Windows) the file must be opened with 'b' included in fopen(3) mode parameter. <?php $filename = "c:\files\somepic.gif"; $handle = fopen($filename, "rb"); $contents = fread($handle, filesize($filename)); fclose($handle); ?> Example #3 Remote fread(3) examples Warning When reading from anything that is not a regular local file, such as streams returned when reading remote files or from popen(3) and fsockopen(3), reading will stop after a packet is available. This means that you should collect the data together in chunks as shown in the examples below. <?php // For PHP 5 and up $handle = fopen("http://www.example.com/", "rb"); $contents = stream_get_contents($handle); fclose($handle); ?> <?php $handle = fopen("http://www.example.com/", "rb"); if (FALSE === $handle) { exit("Failed to open stream to URL"); } $contents = ''; while (!feof($handle)) { $contents .= fread($handle, 8192); } fclose($handle); ?> NOTES
Note If you just want to get the contents of a file into a string, use file_get_contents(3) as it has much better performance than the code above. Note Note that fread(3) reads from the current position of the file pointer. Use ftell(3) to find the current position of the pointer and rewind(3) to rewind the pointer position. SEE ALSO
fwrite(3), fopen(3), fsockopen(3), popen(3), fgets(3), fgetss(3), fscanf(3), file(3), fpassthru(3), ftell(3), rewind(3). PHP Documentation Group FREAD(3)
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