ftell

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

    ftell — Devuelve la posición de lectura/escritura actual del puntero a un fichero

    Descripción

    ftell(resource $handle): int

    Devuelve la posición del puntero al fichero referido por handle.

    Parámetros

    handle

    El puntero al fichero debe ser válido, y debe apuntar a un fichero abierto con éxito por fopen() o popen(). ftell() da resultados indefinidos para flujos de sólo agregado (abiertos con la bandera "a").

    Valores devueltos

    Devuelve la posición del puntero al fichero referido por handle como un entero; esto es, su índice dentro del flujo de fichero.

    Si se produjo un error, devuelve false.

    Nota: Debido a que el tipo integer de PHP es con signo y muchas plataformas usan enteros de 32 bits, algunas funciones de sistema de ficheros pueden devolver resultados inesperados para ficheros que son mayores de 2 GB.

    Ejemplos

    Ejemplo #1 Ejemplo de ftell()

    <?php

    // abre un fichero y leer algunos datos
    $fp = fopen("/etc/passwd", "r");
    $información = fgets($fp, 12);

    // ¿dónde estamos?
    echo ftell($fp); // 11

    fclose($fp);

    ?>

    Ver también

    • fopen() - Abre un fichero o un URL
    • popen() - Abre un proceso de un puntero a un fichero
    • fseek() - Busca sobre un puntero a un fichero
    • rewind() - Rebobina la posición de un puntero a un archivo

    Found A Problem?

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    User Contributed Notes 8 notes

    up
    7
    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
    up
    2
    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.
    up
    0
    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.
    up
    0
    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.
    up
    0
    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.
    up
    0
    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.
    up
    -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
    up
    -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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