#32889 [Csd]: ftruncate doesn't move the file pointer

ID:          32889
Updated by:  wez@php.net
Reported By: techtonik@php.net
Status:      Closed
Bug Type:    Documentation problem
PHP Version: Irrelevant
New Comment:

The file pointer is not changed at all by PHP when you truncate.
This is consistent with ANSI ftruncate (man ftruncate).

You are responsible for sing explicitly if you require it.



Previous Comments:
------------------------------------------------------------------------

[2005-04-29 16:18:32] vrana@php.net

This bug has been fixed in the documentation's XML sources. Since the
online and downloadable versions of the documentation need some time
to get updated, we would like to ask you to be a bit patient.

Thank you for the report, and for helping us make our documentation
better.

"The file pointer is changed only in append mode. In write mode,
additional fs() call is needed."

------------------------------------------------------------------------

[2005-04-29 13:04:11] techtonik@php.net

Something like "Warning: Truncate doesn't change position of the file
pointer. Adjust the pointer with fs to write to the end of the file
after truncate operation in modes other than "a" and "a+"." ?

Examples:
<?php

$fh = fopen("file.txt","w+");
fwrite($fh, "newfile");  // file contains string 'newfile'
ftruncate($fh, 3);
fs($fh, 0, SEEK_END);
fwrite($fh, "contents"); // file contains 'newcontents'
fclose($fh);

?>

<?php

$fh = fopen("file.txt","w+");
fwrite($fh, "newfile");  // file contains string 'newfile'
ftruncate($fh, 3);

fwrite($fh, "contents"); // file contains 'new    contents'
fclose($fh);

?>

------------------------------------------------------------------------

[2005-04-29 12:22:17] tony2001@php.net

"The file pointer is not changed."
(c) man ftruncate

------------------------------------------------------------------------

[2005-04-29 12:12:57] techtonik@php.net

On the second thought it doesn't seem like a feature.

------------------------------------------------------------------------

[2005-04-29 11:36:13] techtonik@php.net

Description:
------------
Note or warning here?

http://www.php.net/manual/en/function.ftruncate.php

Reproduce code:
---------------
<?php

// truncate doesn't move the file pointer to the end of the file

$flog = fopen("text.txt", "w+");
fwrite($flog, "veeery veeery long string");
fs($flog, -2, SEEK_END);
ftruncate($flog, 6);

fwrite($flog, "shortstr");
fclose($flog);

?>

Expected result:
----------------
0000000000: 76 65 65 65 72 79 20 73 │ 68 6F 72 74 73 74 72
veeery shortstr

Actual result:
--------------
0000000000: 76 65 65 65 72 79 20 00 │ 00 00 00 00 00 00 00 00
veeery
0000000010: 00 00 00 00 00 00 00 73 │ 68 6F 72 74 73 74 72
shortstr


------------------------------------------------------------------------


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