gzread

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

gzread — Lectura de archivo gz segura a nivel binario

Descripción

gzread(resource $stream, int $length): string|false

gzread() lee los bytes hasta el parámetro length desde el apuntador al archivo gz dado. La lectura se detiene cuando los bytes del parámetro length (sin comprimir) sean leídos o cuando se alcance el fin del archivo (EOF), lo que ocurra primero.

Parámetros

stream: El apuntador al archivo gz. Debe ser válido y debe apuntar a un archivo abierto exitosamente por gzopen().
length: El número de bytes a leer.

Valores devueltos

Los datos que han sido leídos, o false en caso de error.

Historial de cambios

Versión	Descripción
7.4.0	Esta función ahora devuelve `false` en caso de fallo; antes se devolvía `0`.

Ejemplos

Ejemplo #1 Ejemplo de gzread()

<?php
// pasar los contenidos de un archivo gz a una cadena
$filename = "/usr/local/something.txt.gz";
$zd = gzopen($filename, "r");
$contents = gzread($zd, 10000);
gzclose($zd);
?>

Ver también

gzwrite() - Escritura en un archivo gz, segura a nivel binario
gzopen() - Abre un archivo gz
gzgets() - Obtiene la línea del apuntador al archivo
gzgetss() - Obtiene la línea del apuntador al archivo gz y retira las etiquetas HTML
gzfile() - Lee un archivo gz completo en una matriz
gzpassthru() - Muestra todos los datos restantes a partir del apuntador al achivo gz

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User Contributed Notes 9 notes

down

Nitrogen ¶

12 years ago


Here is a function for returning the uncompressed filesize of a gzip file. The filesize is stored as a 32-bit integer in the end of the compressed file, that's how this function works. Additionally, this function checks to see if it's a real gzip compressed file before doing the work; if it isn't, then just like other gz- functions, it'll treat it just like a regular file and perform a normal filesize operation. Enjoy!

<?php

function gzfilesize($filename) {
  $gzfs = FALSE;
  if(($zp = fopen($filename, 'r'))!==FALSE) {
    if(@fread($zp, 2) == "\x1F\x8B") { // this is a gzip'd file
      fseek($zp, -4, SEEK_END);
      if(strlen($datum = @fread($zp, 4))==4)
        extract(unpack('Vgzfs', $datum));
    }
    else // not a gzip'd file, revert to regular filesize function
      $gzfs = filesize($filename);
    fclose($zp);
  }
  return($gzfs);
}

?>

down

waldermort at gmail dot com ¶

7 years ago


Be careful when reading data in a loop. gzread() behaves a little differently than bzread() or fread(), it does NOT return false when reading past the end of stream. It instead returns an empty string.

So a loop like:
$handle = gzopen($file);
while (false !== $chunk = gzread($handle, $bytes)) {
   //...
}

will loop indefinitely.

down

utku ¶

16 years ago


I don't think it would be wise to open a whole gzip file (it _is_ compressed for a reason, and likely to be a very big file) into a single string. You would most likely hit the php memory limits. Instead, if you need to process the file, put your gzread calls in a loop, and read incrementally by a setting $length to a constant value.

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robinv12001 at yahoo dot co dot in ¶

15 years ago


<?php

//Using FTP Download a gzip file on current date from a remote server

//The gzip files are extracted

function parse_rawlist( $array )

{

    $i=0;

    foreach($array as $curraw)

    {

        $struc = array();

        $current = preg_split("/[\s]+/",$curraw,9);



        $struc['perms']      =     $current[0];

        $struc['number']     =     $current[1];

        $struc['owner']     =     $current[2];

        $struc['group']      =     $current[3];

        $struc['size']         =     $current[4];

        $struc['month']      =     $current[5];

        $struc['day']        =     $current[6];

        $struc['time']      =     $current[7];

        $struc['zfile_name']      =     $current[8];

     $structure[$i]      =     $struc;

    $i++;

    }

   return $structure;



}

ini_set('memory_limit', '100M');



//Give FTP Information Here

//------------------------------------------------------------

$ftp_server     =     "example.com";

$ftp_user_name    =    "example";

$ftp_user_pass    =    "test";

//------------------------------------------------------------

//------------------------------------------------------------

$local_path     =    '/opt/lampp/htdocs/sample/test.gz';//Local Path

$server_path     =     'outgoing/folder/';//Remote Sever Path

//------------------------------------------------------------



$conn_id = ftp_connect($ftp_server,21);

if($conn_id)

{

    echo "Successfully connected";

}

  

$login_result     =     ftp_login($conn_id, $ftp_user_name, $ftp_user_pass);

ftp_chdir($conn_id, $server_path);//Change Current Working Directory

$file_list     =    ftp_rawlist($conn_id,".");

$zip_details    =    parse_rawlist($file_list);

set_time_limit(1000); 

$curr_date    =    strtotime(date("F d Y"));

for($i=0;$i<count($zip_details);$i++)

{

    $fname        =    $zip_details[$i]['zfile_name'];    

    $mod_date1    =    $zip_details[$i]['month']." ".$zip_details[$i]['day']." ".date("Y");    

    $mod_date    =    strtotime($mod_date1);//File Modified Date

    if($mod_date == $curr_date)//If modified date equals current date

    {

        $local_file    =    $fname;

        $server_file    =    $fname;

        if (ftp_get($conn_id, $local_file, $server_file, FTP_BINARY)) 

        {

        

            echo "<br/>Successfully written to $local_file\n";

        } 

        else 

        {

            echo "<br/>There was a problem\n";

        }

        if(file_exists($local_file))

        {

            $fzip_size    =    $zip_details[$i]['size'];    

            $filename    =    $local_file;

            $ext        =    pathinfo($filename,PATHINFO_EXTENSION);    

            $file_name    =    pathinfo($filename,PATHINFO_FILENAME);        

            $file_name    =    $file_name.".csv";

            $zd         =     gzopen($filename, "r");

            $contents     =     gzread($zd, $fzip_size);

            $file_name    =    "uploads/".$file_name;

            file_put_contents($file_name,addslashes($contents));

            if(file_exists($file_name))

            {

                chmod($file_name,0755);

                unlink($local_file);

            }

            gzclose($zd);

        }

    }

}

ftp_close($conn_id);

?>

down

imp ¶

1 year ago


The maximum $length is 2147483647 bytes (2^32-1).

Otherwise gzread() return false.

down

denis at bitrix dot ru ¶

14 years ago


Note that this functions' behavior differs from fread in case of EOF.

When you read the last chunk (mean the last bytes from file), it is EOF just after gzread, but in case of fread you need to read once more to get EOF.

Hope, I am clear :)

down

robinv12001 at yahoo dot co dot in ¶

15 years ago


<?php
//Extracting the content of a gzip file in php and creating a new csv file using the content
//Create a folder uploads inside current folder
$local_file    =    'test.gz';

//To Get the size of the uncompressed file
$FileRead = $local_file;
$FileOpen = fopen($FileRead, "rb");
fseek($FileOpen, -4, SEEK_END);
$buf = fread($FileOpen, 4);
$GZFileSize = end(unpack("V", $buf));
fclose($FileOpen);
//To Get the size of the zip file

$fzip_size    =    $GZFileSize;
    
$filename    =    $local_file;
$ext        =    pathinfo($filename,PATHINFO_EXTENSION);    
$file_name    =    pathinfo($filename,PATHINFO_FILENAME);        
$file_name    =    $file_name.".csv";

$zd         =     gzopen($filename, "rb");
$contents     =     gzread($zd, $fzip_size);
gzclose($zd);
$file_name    =    "uploads/".$file_name;
$fp    =    fopen($file_name, "wb");
fwrite($fp, $contents); //write contents of feed to cache file
fclose($fp);
if(file_exists($file_name))
{
    chmod($file_name,0755);
    unlink($local_file);
}
?>

down

zaotong at yahoo dot com ¶

17 years ago


As was shown to me in another forum there is a way to get the uncompressed size of the gz file by viewing the last 4 bytes of the gz file.

Here is a piece of code that will do this
<?php
$FileRead = 'SomeText.txt';
$FileOpen = fopen($FileRead, "rb");
        fseek($FileOpen, -4, SEEK_END);
        $buf = fread($FileOpen, 4);
        $GZFileSize = end(unpack("V", $buf));
        fclose($FileOpen);
        $HandleRead = gzopen($FileRead, "rb");
        $ContentRead = gzread($HandleRead, $GZFileSize);
?>

This will read the last 4 bytes of the gz file and use it as the file int for the gzread.

Thanks to stereofrog for helping me with this code.

down

-3

calin_ip at yahoo dot com ¶

13 years ago


Regarding finding out the lenght of the gz file.
For some reason the seek() function didn't worked, so, I've tried finding out the last 4 bytes using string functions.
That worked pretty well. Here is the code. 
<?php
$stringu='my_beautiful_file.txt.gz';
$gzip=file_get_contents($stringu);
$rest = substr($gzip, -4); 
$GZFileSize = end(unpack("V", $rest));

$FileRead = $stringu;
$HandleRead = gzopen($FileRead, "rb");
$ContentRead = gzread($HandleRead, $GZFileSize);
gzclose($HandleRead);
?>

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