PHP: ftell - Manual

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Last updated: Sat, 27 Jan 2007

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# ftell

(PHP 3, PHP 4, PHP 5)

ftell -- Сообщает текущее смещение чтения/записи файла

## Описание

int ftell ( resource handle )

Возвращает смещение файлового указателя, ассоциируемого с `handle`.

При возникновении ошибки, возвращает `FALSE`.

Файловый указатель должен быть действующим указателем на поток, открытый функциями fopen() или popen(). ftell() возвращает неопределённые результаты для потоков "дописать в конец" (открытых с флагом "a" flag).

Пример 1. Пример использования функции ftell()

`<?php
// открываем файл и читаем немного данных
$fp = fopen("/etc/passwd", "r");
$data = fgets($fp, 12);
// где же мы ?
echo ftell($fp); // 11
fclose($fp);
?>`

См. также описание функций fopen(), popen(), fseek() и rewind().

add a note User Contributed Notes
ftell
missilesilo at gmail dot com
27-Feb-2007 03:02
`In response to php at michielvleugel dot com:
This does not seem to be the case with PHP 5.2.0 and FreeBSD 5.4.
#!/usr/local/bin/php
<?php
$tell = ftell(STDIN);
var_dump($tell);
?>
root@localhost:/home/david# echo Hello World | ./test.php
int(0)
root@localhost:/home/david# ./test.php
int(6629927)
When something is piped to the script, it returns an integer value of 0, however, it also returns an integer when nothing is piped to the script.
The code should be modified to this:
#!/usr/local/bin/php
<?php
$tell = ftell(STDIN);
if ($tell === 0)
echo "Something was piped: " . fread(STDIN,256) . "\n";
else
echo "Nothing was piped\n";
?>
And the result is:
root@localhost:/home/david# echo Hello World | ./test.php
Something was piped: Hello World
root@localhost:/home/david# ./test.php
Nothing was piped`
mbirth at webwriters dot de
21-Oct-2005 11:09
`Attention! If you open a file with the "text"-modifier (e.g. 'rt') and the file contains \r\n as line-endings, ftell() returns the position as if there were only \n as line-endings.
Example:
If the first line only contains 1 char followed by \r\n, the start of the second line should be position 3. (1char + \r + \n = 3 bytes) But ftell() will return 2 - ignoring one byte. If you call ftell() in line 3, the value will differ from the real value by 2 bytes. The error gets greater with every line.
(Watched this behavior in PHP 5.0.4 for Windows.)
BUT: fseek() works as expected - using the true byte values.`
mweierophinney at gmail dot com
21-Jun-2005 10:00
`Actually, ftell() gives more than an undefined result for append only streams; it gives the offset from the end of the file as defined before any data was appended. So if you open a file that had 3017 characters, and append 41 characters, and then execute ftell(), the value returned will be 41.`
php at michielvleugel dot com
01-Jun-2005 03:19
`When trying to determine whether or not something was piped into a command line script, it is not smart to do a fgets(STDIN), because it will wait indefenitely if nothing is piped. Instead, I found ftell on STDIN to be very handy: it will return an integer of zero when something was piped, and nothing if nothing was piped to the script.
#!/usr/bin/php4 -q
<?
#following will hang if nothing is piped:
#$sometext = fgets(STDIN, 256)
$tell = ftell(STDIN);
if (is_integer($tell)==true)
{echo "Something was piped: ".fread(STDIN,256)."\n";}
else
{echo "Nothing was piped\n";}
?>`
add a note
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Last updated: Sat, 27 Jan 2007
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