chmod

说明

bool chmod ( string filename, int mode )

尝试将 filename 所指定文件的模式改成 mode 所给定的。

注意 mode 不会被自动当成八进制数值，而且也不能用字符串（例如 "g+w"）。要确保正确操作，需要给 mode 前面加上 0：


<?php
chmod("/somedir/somefile", 755);   // 十进制数，可能不对
chmod("/somedir/somefile", "u+rwx,go+rx"); // 字符串，不对
chmod("/somedir/somefile", 0755);  // 八进制数，正确的 mode 值
?>

mode 参数包含三个八进制数按顺序分别指定了所有者、所有者所在的组以及所有人的访问限制。每一部分都可以通过加入所需的权限来计算出所要的权限。数字 1 表示使文件可执行，数字 2 表示使文件可写，数字 4 表示使文件可读。加入这些数字来制定所需要的权限。有关 UNIX 系统的文件权限可以阅读手册“man 1 chmod”和“man 2 chmod”。


<?php
// Read and write for owner, nothing for everybody else
chmod("/somedir/somefile", 0600);

// Read and write for owner, read for everybody else
chmod("/somedir/somefile", 0644);

// Everything for owner, read and execute for others
chmod("/somedir/somefile", 0755);

// Everything for owner, read and execute for owner's group
chmod("/somedir/somefile", 0750);
?>

如果成功则返回 TRUE，失败则返回 FALSE。

注: 当前用户指的是执行 PHP 的用户。很可能和通常的 shell 或者 FTP 用户不是同一个。在大多数系统下文件模式只能被文件所有者的用户改变。

注: 本函数不能作用于远程文件，被检查的文件必须通过服务器的文件系统访问。

注: 当安全模式打开的时候，PHP 会检查所操作的文件是否和正在执行的脚本具有相同的 UID （所有者）。要注意的是，不能修改 SUID，SGID 和 sticky bits。

参见 chown() 和 chgrp()。

add a note User Contributed Notes

NeoSmart Technologies
25-Jul-2006 06:08


The program mentioned below (CHMOD-Win) has been rewritten since, and CHMOD-Win version 3.0 is available for download at http://neosmart.net/dl.php?id=4



It is a conversion utility for CHMOD on Windows and ACL on Linux, comes in handy for installing commercial scripts or defining security policies.

neil at 11 out of 10
12-Apr-2006 03:20


If you get a warning like chmod(): Operation not permitted in /home/folder/public_html/admin/includefiles/fileupload.php on line 24



You can use the ftp_site() function to send a CHMOD command through.

<?php



$ftp_details['ftp_user_name'] = $row['username'];

$ftp_details['ftp_user_pass'] = $row['password'];

$ftp_details['ftp_root'] = '/public_html/';

$ftp_details['ftp_server'] = 'ftp'.$_SERVER['HTTP_HOST'];



function chmod_11oo10($path, $mod, $ftp_details)

{

    // extract ftp details (array keys as variable names)

    extract ($ftp_details);

    

    // set up basic connection

    $conn_id = ftp_connect($ftp_server);

    

    // login with username and password

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

    

    // try to chmod $path directory

    if (ftp_site($conn_id, 'CHMOD '.$mod.' '.$ftp_root.$path) !== false) {

        $success=TRUE;

    } 

    else {

        $success=FALSE;

    }



    // close the connection

    ftp_close($conn_id);

    return $success;

}

?>

The key thing to remember is that the document root and the ftp root are not the same.

e.g. document root may be "/home/folder/public_html/"

but the ftp root might be "/public_html/"



Hope this helps someone.  You might need this solution if you are on a shared server.

memp
23-Aug-2005 06:04


If you are storing your mode in a variable like



$mode = 0755;



you will run into the inevitable octal mode problem.  An easy way around that is to use the octdec() function.



chmod("some_filename.ext", octdec($mode));

masha at mail dot ru
11-Jul-2005 12:23


Usefull reference:



Value    Permission Level

400    Owner Read

200    Owner Write

100    Owner Execute

40    Group Read

20    Group Write

10    Group Execute

4    Global Read

2    Global Write

1    Global Execute



(taken from http://www.onlamp.com/pub/a/php/2003/02/06/php_foundations.html)

alex at feidesign dot com
01-Apr-2005 08:20


If you cannot chmod files/directories with PHP because of safe_mode restrictions, but you can use FTP to chmod them, simply use PHP's FTP-functions (eg. ftp_chmod or ftp_site) instead. Not as efficient, but works.

info at rvgate dot nl
03-Feb-2005 09:12


When using ftp_rawlist, in order to get the chmod number from the attributes, i use this code:



<?php

function chmodnum($mode) {

    $realmode = "";

    $legal =  array("","w","r","x","-");

    $attarray = preg_split("//",$mode);

    for($i=0;$i<count($attarray);$i++){

        if($key = array_search($attarray[$i],$legal)){

            $realmode .= $legal[$key];

        }

    }

    $mode = str_pad($realmode,9,'-');

    $trans = array('-'=>'0','r'=>'4','w'=>'2','x'=>'1');

    $mode = strtr($mode,$trans);

    $newmode = '';

    $newmode .= $mode[0]+$mode[1]+$mode[2];

    $newmode .= $mode[3]+$mode[4]+$mode[5];

    $newmode .= $mode[6]+$mode[7]+$mode[8];

    return $newmode;

}

?>

some examples:



drwxr-xr-x => 755

drwxr-xr-x => 755

dr-xr-xr-x => 555

drwxr-xr-x => 755

drwxr-xr-x => 755

drwxr-xr-x => 755

drwxr-xr-x => 755

drwxrwxrwt => 776

drwxr-xr-x => 755

drwxr-xr-x => 755

lrwxrwxrwx => 777



used some of already posted code...

haasje at welmers dot net
28-Nov-2004 04:09


For recursive chmod'ing see the function below.

Only really usefull when chmod'ing a tree containing directories only, jet, since you don't want an executable bit on a regular file. Who completes the function so it's accepting strings like "g+w", and it's as usefull as unix "chmod -R" ? ;-)



<?php



function chmod_R($path, $filemode) { 

    if (!is_dir($path))

       return chmod($path, $filemode);



    $dh = opendir($path);

    while ($file = readdir($dh)) {

        if($file != '.' && $file != '..') {

            $fullpath = $path.'/'.$file;

            if(!is_dir($fullpath)) {

              if (!chmod($fullpath, $filemode))

                 return FALSE;

            } else {

              if (!chmod_R($fullpath, $filemode))

                 return FALSE;

            }

        }

    }

 

    closedir($dh);

    

    if(chmod($path, $filemode))

      return TRUE;

    else 

      return FALSE;

} 

?>

PerfectWeb
23-Nov-2004 11:58


As noted by others below... 1) you cannot pass a string to chmod() as the mode, and 2) decimals work as well as octals for the mode.



If you need to come up with the mode on the fly (maybe based on user input) and want to use something like:



$mode = '0'.$owner.$group.$public;



you can use your $mode (which is a string) with chmod like this:



<?php

 // octal mode in a string i.e. '0755'

 $mode = '0'.$owner.$group.$public;



 $mode_dec = octdec($mode);    // convert octal mode to decimal

 chmod($filename, $mode_dec);

?>

fernando at gym-group dot com
12-Nov-2004 11:10


about chmod,

Problably you have a local server to simulate your scripts before upload them to the server. No matter if you use Apache under windows or IIS ,  a chmod instruction like chmod($filename,O777) may not work because windows does not handle that kind of permission's format.

So being in your local server, if you have a only read file and you try to erase, it will show that you dont have permissions even when you have already executed your chmod instrucction correctly. Just up the script it must work well in your internet server if it is a linux machine



sobre chmod,

Probablemente usas un servidor local para probar tus scripts antes de subirlos al servidor en internet. No importa si usas Apache bajo windows o IIS, una instruccion como chmod(nombre_archivo,O777) podr no trabajar por que windows no maneja esa estructura para definir los permisos.

Estando en tu servidor local, si tienes un archivo de solo lectura y tratas de borrarlo,  se mostrar un error diciendo que no tienes permisos an despes de haber ejecutado chmod correctamente. Sube tu script, si tu servidor es una mquina linux, el script trabajar sin problemas en internet.



Fernando Yepes C.

Oliver Hankeln
01-Jul-2004 11:21


Well, you don't need octals.

You need a value that can easily computed and remembered if printed in octal. 

511 (decimal) is the same as 777 (octal).

So it's the same wether you write

chmod("foo",511)

or 

chmod("foo",0777)



The latter is just better readable.

raven_25041980 at yahoo dot com
25-May-2004 01:45


If you have a mode as a string, chmod will insanely mess up your permissions. Instead of using 



<?php 



@chmod($file_or_dir_name, $mode);



?>



use 



<?php 



@chmod(file_or_dir_name, intval($mode, 8));



?>



where 8 -> the base to convert into. You need octals, baby, for chmod...



More on intval here: http://www.php.net/manual/en/function.intval.php

agrenier at assertex dot com
02-Apr-2004 09:17


If you find that chmod does not work on your file and that a new file cannot be created, first try to chmod the directory where the file is being created to 0666/0777. Then PHP should be able to write/append files with mode 0644.

agrenier at assertex dot com
02-Apr-2004 09:11


This function will chmod a $filename before writing to it if:



1 - It exists

2 - It is not writeable

3 - PHP has permission to chmod files



If PHP can't chmod, then the script will end. Otherwise it will attempt to write to a new file.



<?php



    function file_write($filename, $flag, &$content) { 

        if (file_exists($filename)) {

            if (!is_writable($filename)) {

                if (!chmod($filename, 0666)) {

                     echo "Cannot change the mode of file ($filename)";

                     exit;

                };

            }

        }

        if (!$fp = @fopen($filename, $flag)) {

            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;

        }

    }



?>

Jazeps Basko
27-Jan-2004 11:37


To convert 'rwxr-xr--' to a number representation of chmod, i use this:

<?php

    function chmodnum($mode) {

        $mode = str_pad($mode,9,'-');

        $trans = array('-'=>'0','r'=>'4','w'=>'2','x'=>'1');

        $mode = strtr($mode,$trans);

        $newmode = '';

        $newmode .= $mode[0]+$mode[1]+$mode[2];

        $newmode .= $mode[3]+$mode[4]+$mode[5];

        $newmode .= $mode[6]+$mode[7]+$mode[8];

        return $newmode;

    }

?>

pmichaud at pobox dot com
20-Apr-2003 06:45


In the previous post, stickybit avenger writes:


    Just a little hint. I was once adwised to set the 'sticky bit', i.e. use 1777 as chmod-value...





Note that in order to set the sticky bit on a file one must use '01777' (oct) and not '1777' (dec) as the parameter to chmod:





<?php


    chmod("file",01777);   // correct


     chmod("file",1777);    // incorrect, same as chmod("file",01023), causing no owner permissions!


?>





Rule of thumb: always prefix octal mode values with a zero.

sticky bit avenger
12-Mar-2003 07:30


Just a little hint. I was once adwised to set the 'sticky bit', i.e. use 1777 as chmod-value. Do NOT do this if you don't have root privileges. When 'sticky bit' is set ONLY the fileuser can delete it afterwards, typically 'httpd' or something like that in case of an upload-script for example. I was unaware of this and actually had to make a script for deleting these files as I could not do this from ftp/ssh even though I did have read/write/execute access to both files and folders. Use simply '0777' or similiar.

Half-Dead at nospam dot com
08-Nov-2002 06:42


[Editor's note:


That is due the fact Win32 systems treat premissions. You do not really have any other levels but read-only.





Maxim]








On WinME with apache chmod also works to a certain limit.





What happens is that apparently only the first number is counted, so 0666 (read-write) is the same as 0777, 0644, 0600, etc, and 0444 (read-only) is the same as 477, 400, etc.





..didn't test 0500 series

FF7Cayn at gmx dot de
28-Oct-2001 08:09


It does work on Windows.


I use Win 98 with the Sambar Server.


The only chmods allowed are the 775 and 666 mod. 775 for non-writeable and 666 for writeable. The only thing is that the usergroups doesn't work.


Note: the 0 at the start doesn't work with windows. use only the decimal kind.


Have fun :)

jon at zend dot com
15-Oct-2001 11:37


if 'mode' is held in a variable and is and octal value you need to convert it to decimal before passing it to the function:


chmod ($filename, octdec($mode))

gnettles2 at home dot com
25-Aug-2001 02:20


Usually when you're trying to write to af file, you'll need to chmod the file to something like 666 or 755. You can use a command to chmod the file for you, which is especially useful when you're making a script where you're setting it up so that your users don't have to peform a bunch of actions to setup the script. When i wrote my news program script, I only had two files. install.php and config.php. All you had to do was chmod install.php to 666 and open it up in a web browser and answer a few questions. The script itself setup the rest of the files and chmodded them for you.

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