ftell

(PHP 4, PHP 5, PHP 7, PHP 8)

ftell — Dosya okuma/yazma konumlayıcının mevcut konumu ile döner

Açıklama

ftell(resource $dt): int|false

Dosya tanıtıcısı dt ile belirtilen dosyadaki dosya konumlayıcının konumunu döndürür.

Bağımsız Değişkenler

dt: Dosya tanıtıcısı geçerli olmalı ve fopen() veya popen() tarafından başarıyla açılmış bir dosya için döndürülmüş olmalıdır. ftell() işlevi sadece ekleme kipinde ('a' seçeneği ile) açılmış akımlarda yanlış sonuçlar verebilir.

Dönen Değerler

Dosya tanıtıcısı dt ile belirtilen dosyadaki dosya konumlayıcının konumunu (dosyanın başlangıcına göre) döndürür.

Bir hata oluşursa false döner.

Bilginize: PHP'nin tamsayı türü, işaretli tamsayı türü olduğundan 32 bitlik tamsayıların kullanıldığı sistemlerde bazı dosya sistemi işlevleri 2GB'tan büyük dosyalarda beklenmedik sonuçlar verebilir.

Örnekler

Örnek 1 - ftell() örneği

<?php

// Bir dosya açıp biraz veri okuyalım
$fp = fopen("/etc/passwd", "r");
$data = fgets($fp, 12);

// Bakalım neredeyiz?
echo ftell($fp); // 11

fclose($fp);

?>

Ayrıca Bakınız

fopen() - Bir dosya veya URL'yi açar
popen() - Bir süreç tanıtıcısı açar
fseek() - Dosya tanıtıcısında konumu bir yerden başka bir yere taşır
rewind() - Bir dosya tanıtıcısında konumu başa taşır

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User Contributed Notes 8 notes

down

Mindaugas ¶

9 years ago

When opening a file for reading and writing via fopen('file','a+') the file pointer should be at the end of the file. However ftell() returns int(0) even if the file is not empty. Also it seems that there is two pointers, first for reading and second for writing, because it acts differently on first operation (reading or writing).

Example:
<?php
$file = fopen('counter.txt', 'w');
fwrite($file, '123456789');
fclose($file);

$file = fopen('counter.txt', 'r');
echo ftell($file) . ' "' . fgets($file) . '" ' . ftell($file) . PHP_EOL;
fclose($file);

$file = fopen('counter.txt', 'a+');
echo ftell($file) . ' "' . fgets($file) . '" ' . ftell($file) . PHP_EOL;
fclose($file);

$file = fopen('counter.txt', 'r+');
fwrite($file, 'rr');
echo ftell($file) . ' "' . fgets($file) . '" ' . ftell($file) . PHP_EOL;
fclose($file);

$file = fopen('counter.txt', 'a+');
fwrite($file, 'aa');
echo ftell($file) . ' "' . fgets($file) . '" ' . ftell($file) . PHP_EOL;
fclose($file);

$file = fopen('counter.txt', 'r');
echo ftell($file) . ' "' . fgets($file) . '" ' . ftell($file) . PHP_EOL;
fclose($file);
?>

Result:
0 "123456789" 9
0 "123456789" 9
2 "3456789" 9
2 "" 2
0 "rr3456789aa" 11

down

burninleo at gmx dot net ¶

15 years ago

When opening a file to append via fopen('file','ab') the file pointer should be at the end of the file. However ftell() returns int(0) even if the file is not empty and even after writing some text into the file.

down

d9k at ya dot ru ¶

2 years ago

Had to use 

<?php
posix_isatty(STDIN) == false
?>

instead of 

<?php
ftell(STDIN) !== false
?>

after upgrade from php 7 to 8 on ubuntu.

down

d9k at ya dot ru ¶

2 years ago

Had to use 

<?php
posix_isatty(STDIN) == false
?>

instead of 

<?php
ftell(STDIN) !== false
?>

after upgrade from php 7 to 8 on ubuntu.

down

mbirth at webwriters dot de ¶

19 years ago

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.

down

mweierophinney at gmail dot com ¶

19 years ago

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.

down

-2

missilesilo at gmail dot com ¶

17 years ago

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

down

-2

php at michielvleugel dot com ¶

19 years ago

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";}

?>

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