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is_writeable> <is_uploaded_file
[edit] Last updated: Sat, 12 May 2012

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is_writable

(PHP 4, PHP 5)

is_writableTells whether the filename is writable

Description

bool is_writable ( string $filename )

Returns TRUE if the filename exists and is writable. The filename argument may be a directory name allowing you to check if a directory is writable.

Keep in mind that PHP may be accessing the file as the user id that the web server runs as (often 'nobody'). Safe mode limitations are not taken into account.

Parameters

filename

The filename being checked.

Return Values

Returns TRUE if the filename exists and is writable.

Examples

Example #1 is_writable() example

<?php
$filename 
'test.txt';
if (
is_writable($filename)) {
    echo 
'The file is writable';
} else {
    echo 
'The file is not writable';
}
?>

Errors/Exceptions

Upon failure, an E_WARNING is emitted.

Notes

Note: The results of this function are cached. See clearstatcache() for more details.

Tip

As of PHP 5.0.0, this function can also be used with some URL wrappers. Refer to Supported Protocols and Wrappers to determine which wrappers support stat() family of functionality.

See Also



is_writeable> <is_uploaded_file
[edit] Last updated: Sat, 12 May 2012
 
add a note add a note User Contributed Notes is_writable
gr 05-Oct-2010 03:32
The results of this function seems to be not cached :
Tested on linux and windows

<?php
chmod
($s_pathFichier, 0400);
echo
'<pre>';var_dump(is_writable($s_pathFichier));echo'</pre>';
chmod($s_pathFichier, 04600);
echo
'<pre>';var_dump(is_writable($s_pathFichier));echo'</pre>';
exit;
?>
starrychloe at yahoo dot com 10-Feb-2008 05:50
To Darek and F Dot: About group permissions, there is this note in the php.ini file:
; By default, Safe Mode does a UID compare check when
; opening files. If you want to relax this to a GID compare,
; then turn on safe_mode_gid.
safe_mode_gid = Off
wuhai 25-Sep-2007 09:46
I was trying to create a new file using fwrite, and i had the following error.  Any idea?
Warning: fwrite(): supplied argument is not a valid stream resource in
legolas558 d0t users dot sf dot net 02-Mar-2007 12:18
This is the latest version of is__writable() I could come up with.
It can accept files or folders, but folders should end with a trailing slash! The function attempts to actually write a file, so it will correctly return true when a file/folder can be written to when the user has ACL write access to it.

<?php
function is__writable($path) {
//will work in despite of Windows ACLs bug
//NOTE: use a trailing slash for folders!!!
//see http://bugs.php.net/bug.php?id=27609
//see http://bugs.php.net/bug.php?id=30931

   
if ($path{strlen($path)-1}=='/') // recursively return a temporary file path
       
return is__writable($path.uniqid(mt_rand()).'.tmp');
    else if (
is_dir($path))
        return
is__writable($path.'/'.uniqid(mt_rand()).'.tmp');
   
// check tmp file for read/write capabilities
   
$rm = file_exists($path);
   
$f = @fopen($path, 'a');
    if (
$f===false)
        return
false;
   
fclose($f);
    if (!
$rm)
       
unlink($path);
    return
true;
}
?>
haccel at email dot com 03-Aug-2006 05:51
Ooooops, sorry! My mistake. is__writable should be:

<?php

function is__writable($path)
{

   if (
$path{strlen($path)-1}=='/') //Start function again with tmp file...
     
      
return is__writable($path.uniqid(mt_rand()).'.tmp');
 
   elseif (
ereg('.tmp', $path))
   {
//Check tmp file for read/write capabilities
     
      
if (!($f = @fopen($path, 'w+')))
           return
false;
      
fclose($f);
      
unlink($path);
       return
true;

   }
   else
//We have a path error.
     
      
return 0; // Or return error - invalid path...

}

?>

The original could've deleted a folder if the path was invalid  to start with (no trailing slash..) and the folder was writable to begin with...
haccel at email dot com 02-Aug-2006 08:56
Be careful of legolas558 dot sourceforge comma net's example, try this instead:

<?php

function is__writable($path)
{

    if (
$path{strlen($path)-1}=='/')
       
        return
is__writable($path.uniqid(mt_rand()).'.tmp');
   
    elseif (
file_exists($path) && ereg('.tmp', $path))
    {
       
        if (!(
$f = @fopen($path, 'w+')))
            return
false;
       
fclose($f);
       
unlink($path);
        return
true;

    }
    else
       
        return
0; // Or return error - invalid path...

}

?>
legolas558 dot sourceforge comma net 13-Jul-2006 01:17
Since looks like the Windows ACLs bug "wont fix" (see http://bugs.php.net/bug.php?id=27609) I propose this alternative function:

<?php

function is__writable($path) {

if (
$path{strlen($path)-1}=='/')
    return
is__writable($path.uniqid(mt_rand()).'.tmp');

if (
file_exists($path)) {
    if (!(
$f = @fopen($path, 'r+')))
        return
false;
   
fclose($f);
    return
true;
}

if (!(
$f = @fopen($path, 'w')))
    return
false;
fclose($f);
unlink($path);
return
true;
}

?>

It should work both on *nix and Windows

NOTE: you must use a trailing slash to identify a directory
Nils Kuebler 18-Apr-2006 03:15
this one recursivly checks if a folder and all its contents are writeable

<?php
function is_removeable($dir)
{
  
$folder = opendir($dir);
   while(
$file = readdir( $folder ))
    if(
$file != '.' && $file != '..' &&
        ( !
is_writable$dir."/".$file  ) ||
        ( 
is_dir(   $dir."/".$file   ) && !is_removeable(   $dir."/".$file   )  ) ))
   {
   
closedir($dir);
    return
false;
   }
  
closedir($dir);
   return
true;
}
?>
greg at gregwhitescarver dotcalm 07-Feb-2006 06:55
In response to Darek:

We have two servers: one running PHP 5.0.4 and Apache 1.3.33, the other running PHP 4.3.5 and Apache 1.3.27.  The PHP 4 server exhibits the behavior you are describing, with is_writable() returning 'false' even though the www user is in the group that owns the file, but the PHP 5 server is returning 'true.'
darek at fauxaddress dot com 31-Jan-2006 10:27
It appears that is_writable() does not check full permissions of a file to determine whether the current user can write to it.  For example, with Apache running as user 'www', and a member of the group 'wheel', is_writable() returns false on a file like

-rwxrwxr-x           root         wheel          /etc/some.file
JimmyNighthawk 12-Sep-2005 02:02
Regarding you might recognize your files on your web contructed by your PHP-scripts are grouped as NOBODY you can avoid this problem by setting up an FTP-Connection ("ftp_connect", "ftp_raw", etc.) and use methods like "ftp_fput" to create these [instead of giving out rights so you can use the usual "unsecure" way]. This will give the files created not the GROUP NOBODY - it will give out the GROUP your FTP-Connection via your FTP-Program uses, too.

Furthermore you might want to hash the password for the FTP-Connection - then check out:
http://dev.mysql.com/doc/mysql/en/Password_hashing.html
claude dot paroz at ne dot ch 06-Apr-2004 04:28
Under Windows, it only returns the read-only attribute status, not the actual permissions (ACL).
See http://bugs.php.net/bug.php?id=27609
agrenier at assertex dot com 02-Apr-2004 04:56
This file_write() function will give $filename the write permission before writing $content to it.

Note that many servers do not allow file permissions to be changed by the PHP user.

<?php
   
function file_write($filename, &$content) {
        if (!
is_writable($filename)) {
            if (!
chmod($filename, 0666)) {
                 echo
"Cannot change the mode of file ($filename)";
                 exit;
            };
        }
        if (!
$fp = @fopen($filename, "w")) {
            echo
"Cannot open file ($filename)";
            exit;
        }
        if (
fwrite($fp, $content) === FALSE) {
            echo
"Cannot write to file ($filename)";
            exit;
        }
        if (!
fclose($fp)) {
            echo
"Cannot close file ($filename)";
            exit;
        }
    }
?>

 
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