ftell
I have produced a number of tests below which walk through my findings of the ftruncate function. For the impatient among you ftruncate can be used to increase the size of the file and will fill the rest of the file with CHR 0 or ASCII NULL. It can be used as a very convenient way of making a 1Mb file for instance.
Test 1
<?php
/*
Test 1: Write "some text" to a file.
Result: The text "some text" should be present in test_1.txt
*/
$fp = fopen('test_1.txt', 'w+');
fwrite($fp, 'some text');
?>
The first test is only here to make sure that a file can be written with some text.
Test 2
<?php
/*
Test 2: Write "some text" to a file and ftruncate the file to 4 bytes.
Result: The text "some" should be present in test_2.txt as the file will have been truncated to 4 bytes.
*/
$fp = fopen('test_2.txt', 'w+');
fwrite($fp, 'some text');
ftruncate($fp, 4);
?>
As expected the file has been truncated to 4 bytes.
Test 3
<?php
/*
Test 3: Write "some text" to a file and ftruncate the file to 40 bytes.
Result: The text "some text" should be present in test_3.txt as the file will have been truncated to 40 bytes.
*/
$fp = fopen('test_3.txt', 'w+');
fwrite($fp, 'some text');
ftruncate($fp, 40);
?>
Interestingly the file has increased from 9 bytes to 40 bytes. The remaining 31 bytes of the file are ASCII code 0 or NULL though.
Further notes can be found here http://mikeleigh.com/links/ftruncate
ftruncate
(PHP 4, PHP 5)
ftruncate — Truncates a file to a given length
Description
bool ftruncate ( resource $handle, int $size )Takes the filepointer, handle, and truncates the file to length, size. Returns TRUE on success or FALSE on failure.
Note: The file pointer is changed only in append mode. In write mode, additional fseek() call is needed.
Note: Prior to PHP 4.3.3, ftruncate() returns an integer value of 1 on success, instead of boolean TRUE.
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User Contributed Notesftruncate
mike at mikeleigh dot com
04-Jan-2007 08:30
04-Jan-2007 08:30