Re: [PHP] exec and system do not work

Ethan Rosenberg, PhD
/Pres/CEO/
*Hygeia Biomedical Research, Inc*
2 Cameo Ridge Road
Monsey, NY 10952
T: 845 352-3908
F: 845 352-7566
[email protected]

On 08/26/2013 07:33 PM, David Robley wrote:
> Ethan Rosenberg wrote:
>
>>
>> On 08/26/2013 11:36 AM, [email protected] wrote:
>>>
>>>
>>>> Tamara Temple <[email protected]> hat am 26. August 2013 um 08:33
>>>> geschrieben:
>>>>
>>>>
>>>>
>>>> On Aug 25, 2013, at 10:41 PM, Ethan Rosenberg
>>>> <[email protected]> wrote:
>>>>
>>>>> Dear List -
>>>>>
>>>>> I'm lost on this one -
>>>>>
>>>>> This works -
>>>>>
>>>>> $out = system("ls -l ",$retvals);
>>>>> printf("%s", $out);
>>>>>
>>>>> This does -
>>>>>
>>>>> echo exec("ls -l");
>>>
>>> Please show the output of the directory listing.
>>> Please us "ls -la"
>>>
>>>>>
>>>>> This does not -
>>>>>
>>>>> if( !file_exists("/var/www/orders.txt"));
>>>>> {
>>>>>      $out = system("touch /var/www/orders.txt", $ret);
>>>
>>> Maybe you don't have write permissions on the folder?
>>>
>>>>>      $out2 = system("chmod 766 /var/www/orders.txt", $ret);
>>>>>      echo 'file2<br />';
>>>>>      echo file_exists("/var/www/orders.txt");
>>>>> }
>>>>>
>>>>> and this does not -
>>>>>
>>>>> if( !file_exists("/var/www/orders.txt"));
>>>>> {
>>>>>      exec("touch /var/www/orders.txt");
>>>>>      exec("chmod 766 /var/www/orders.txt");
>>>>>      echo 'file2<br />';
>>>>>      echo file_exists("/var/www/orders.txt");
>>>>> }
>>>>>
>>>>> Ethan
>>>>>
>>>>>
>>>>
>>>> When you say "does not work", can you show what is actually not working?
>>>> I believe the exec and system functions are likely working just fine,
>>>> but that the commands you've passed to them may not be.
>>>>
>>>>
>>>>
>>> --
>>> Marco Behnke
>>> Dipl. Informatiker (FH), SAE Audio Engineer Diploma
>>> Zend Certified Engineer PHP 5.3
>>>
>>> Tel.: 0174 / 9722336
>>> e-Mail: [email protected]
>>>
>>> Softwaretechnik Behnke
>>> Heinrich-Heine-Str. 7D
>>> 21218 Seevetal
>>>
>>> http://www.behnke.biz
>>>
>>
>> Tamara -
>>
>>   > Please show the output of the directory listing.
>>   > Please us "ls -la"
>>
>> echo exec('ls -la orders.txt');
>>
>> -rw-rw-rw- 1 ethan ethan 43 Aug 25 23:50 orders.txt
>>
>>
>> Maybe you don't have write permissions on the folder?
>>
>> If I perform the touch and chmod from the command line, everything works.
>>
>>
>>   >> When you say "does not work", can you show what is actually not
>> working? I
>>   >> believe the exec and system functions are likely working just fine,
>> but that
>>   >> the commands you've passed to them may not be.
>>
>> Here are my commands.
>>
>> if( !file_exists("/var/www/orders.txt"));
>> {
>> echo system("touch /var/www/orders.txt", $ret);
>> echo system("chmod 766 /var/www/orders.txt", $ret);
>> echo 'file2<br />';
>> echo file_exists("/var/www/orders.txt");
>> }
>>
>> If I now try a ls from the command line, the return is
>>    cannot access /var/www/orders.txt: No such file or directory
>>
>> The ls -la  works because the file was created from the command line.
>>
>> TIA
>>
>> Ethan
>
> Note that touch and chmod don't return any output, so echoing the result of
> a system call for those commands will give an empty string.
>
> You should be checking the values of $ret for each execution of system to
> see whether the command was successful or not - the return status of the
> executed command will be written to this variable. I'd guess that touch is
> returning 13 - permission denied.
>
> if( !file_exists("/var/www/orders.txt"))
> {
>    system("touch /var/www/orders.txt", $ret1);
>    echo 'touch returned '.$ret1.'<br> /';
>    system("chmod 766 /var/www/orders.txt", $ret2);
>    echo 'chmod returned ' .$ret2.'<br> /';
>    echo 'file2<br />';
> echo file_exists("/var/www/orders.txt"); }
>
> Check the permissions for directory /var/www; you'll probably find it is
> writable by the user you log on as, but not by the user that apache/php runs
> as, which is often www - a user with limited privileges.
>
> As other(s) have pointed out, there are php functions to do what you want
> without introducing the possible insecurities involved with system et al.
>

David -

touch returned 1
  /chmod returned 1

rosenberg:/var/www# ls orders.txt
ls: cannot access orders.txt: No such file or directory

rosenberg:/var# ls -ld www
drwxr-xr-x 37 ethan ethan 20480 Aug 26 20:15 www

TIA

Ethan