50% CPU usage when using system function

[uprightdog]

I'm attempting to back up a directory using PHP's system() function. My code looks something like this:

$command='tar -cvzf /home/my_username/backups/backed_up_files.tar.gz /home/my_username/public_html/files_to_be_backed_up';

if (system($command) === FALSE) {
$status="Error';
} else {
$status='Success';
}
echo $status;

What happens is this - the archive isn't created, I get neither an error or success message, and the process's CPU usage shoots up to about 50%, and stays there until I kill it manually.

I'm fairly new to using system(), so it could well be the case that I'm unaware of something. Any ideas?

[Ron]

I think it's waiting in tar for a list of files maybe?

I don't see a space between the ".tar" and the "." at the end of the line.
I also don't see a semi colon at the end of the first line. (You probably want to separate those commands into two separate calls anyway, so that you can isolate and report on the problem rather than just "Script encountered some error".)
I am also confused about what you're trying to do to what files in what directory.
I am also confused why you're using both the -z flag and a separate gz step.
There's also a syntax problem with single quotes and double quotes in this script. ( $status="Error'; )

So to answer the 50% question, php might be consuming the resources in a tight loop polling for the tar command to finish. Just a guess.

Also, I'd try to stay away from using words as variables that might be or might become reserved words in the language (or any future language to which you might want to port the applciation.) Words like "command" and "status", for instance.

So let's try this

<?php
// This will create the tarball named backed_up_files.tar
$command_tar='tar -cvf /home/my_username/backups/backed_up_files.tar /home/my/username/directory_to_be_backed_up';

// This will compress backed_up_files.tar and create backed_up_files.tar.gz
$command_gz='gz /home/my_username/public_html/backed_up_files.tar';

$my_status = "Success";
if (system($command_tar) === FALSE)
{
   $my_status="Error in tar command";
}
else 
{
   if (system($command_gz) === FALSE)
   {
      $my_status="Error in gz command";
   }
}
echo $my_status;
?>

You can probably do more with error reporting than I've done here. I don't use very many system() calls in php, and any I've done have been quick hacks, so I haven't done robust error reporting with it.

Good luck!

[uprightdog]

I don't see a space between the ".tar" and the "." at the end of the line.
I also don't see a semi colon at the end of the first line.

Not sure what you mean here - there is a semi-colon. Regardless, the command works fine when used within a cron job - so I'm guessing it must be the something to do with the context in which I'm employing it (system).

I am also confused why you're using both the -z flag and a separate gz step.

As I say, I'm new to system commands, so fumbling my way a bit.

There's also a syntax problem with single quotes and double quotes in this script. ( $status="Error'; )

Just a typo in my post, sorry.

So let's try this

<?php
// This will create the tarball named backed_up_files.tar
$command_tar='tar -cvf /home/my_username/backups/backed_up_files.tar /home/my/username/directory_to_be_backed_up';

// This will compress backed_up_files.tar and create backed_up_files.tar.gz
$command_gz='gz /home/my_username/public_html/backed_up_files.tar';

$my_status = "Success";
if (system($command_tar) === FALSE)
{
   $my_status="Error in tar command";
}
else 
{
   if (system($command_gz) === FALSE)
   {
      $my_status="Error in gz command";
   }
}
echo $my_status;
?>

Your individual commands also work in the context of cron. But when used as arguments in system(), they do nothing. It reports success, and doesn't tie up the CPU. But it doesn't create any archives at all.

[Ron]

First off, PLEASE don't post code if it isn't the code with which you had the problem, or at least label it as not the same code.

Not sure what you mean here - there is a semi-colon.

Ok;, here is your line

$command='tar -cvzf /home/my_username/backups/backed_up_files.tar. gz /home/my_username/public_html/files_to_be_backed_u p'; 

It is trying to issue two commands, a tar command and a gz command. They need to be separated by a semi colon.

Anyway, I ran my version, and it works just fine for me. Are you running this from the command line, or trying to execute it from a browser through the webserver? Do you or your webserver have permissions to write to the directory? Try the code with simple commands like

$command_tar = 'echo "I am in the tar command"> /home/my_username/dirname/tarball.tar'; 

Then you can type

zcat tarball.tar.gz

and you should see

I am in the tar command

Here is a test I ran with the code first; the only changes are to obfuscate my username and directoryname.

<?php
$command_tar='tar -cvf /home/my_username/dirname/tarball.tar /home/my_username/dirname/';

$command_gz='gzip -v /home/my_username/dirname/tarball.tar';
$command_ls='ls -alt /home/my_username/dirname/';
system($command_ls);
$my_status = "Success";
if (system($command_tar) === FALSE)
{
   $my_status="Error in tar command";
}
else
{
   if (system($command_gz) === FALSE)
   {
      $my_status="Error in gz command";
   }
}
echo $my_status;
system($command_ls);
?>

$ php ron.php
total 10848
drwxr-xr-x 3 my_username my_username 4096 Feb 26 08:20 .
drwx--x--x 30 my_username my_username 4096 Feb 26 08:20 ..
-rw-r--r-- 1 my_username my_username 438 Feb 26 08:20 ron.php
-rw-r--r-- 1 my_username my_username 11052773 Jan 28 20:16 ip.txt
-rw-r--r-- 1 my_username my_username 227 Apr 11 2005 index.php
drwxr-xr-x 3 my_username my_username 4096 Jul 22 2004 temp
tar: Removing leading `/' from member names
/home/my_username/dirname/
/home/my_username/dirname/ip.txt
/home/my_username/dirname/index.php
/home/my_username/dirname/ron.php
tar: /home/my_username/dirname/tarball.tar: file is the archive; not dumped
/home/my_username/dirname/temp/
/home/my_username/dirname/temp/bak/
/home/my_username/dirname/temp/bak/3.php
/home/my_username/dirname/temp/bak/1.php
/home/my_username/dirname/temp/bak/2.php
/home/my_username/dirname/temp/3.php
/home/my_username/dirname/temp/1.php
/home/my_username/dirname/temp/ron.awk
/home/my_username/dirname/temp/ron.sed
/home/my_username/dirname/temp/2.php
/home/my_username/dirname/tarball.tar: 93.9% -- replaced with /home/my_username/dirname/tarball.tar.gz
Success
total 11520
drwxr-xr-x 3 my_username my_username 4096 Feb 26 08:20 .
-rw-r--r-- 1 my_username my_username 680012 Feb 26 08:20 tarball.tar.gz
drwx--x--x 30 my_username my_username 4096 Feb 26 08:20 ..
-rw-r--r-- 1 my_username my_username 438 Feb 26 08:20 ron.php
-rw-r--r-- 1 my_username my_username 11052773 Jan 28 20:16 ip.txt
-rw-r--r-- 1 my_username my_username 227 Apr 11 2005 index.php
drwxr-xr-x 3 my_username my_username 4096 Jul 22 2004 temp

[uprightdog]

First off, PLEASE don't post code if it isn't the code with which you had the problem, or at least label it as not the same code.

Fair enough. Apologies.

Anyway, I ran my version, and it works just fine for me. Are you running this from the command line, or trying to execute it from a browser through the webserver? Do you or your webserver have permissions to write to the directory?

It was indeed permissions. Your version now works.

Thanks for your help Ron.

[Ron]

Anytime.

BTW, I don't think that checking for system() === FALSE will do as you're expecting.

Here was output when I forgot to rename my_username/directoryname to the proper values:

sh: /home/my_username/dirname/tarball.tar: No such file or directory
gzip: /home/my_username/dirname/tarball.tar: No such file or directory
Success

You'll have to play around with the commands and their actual return values to get that construct to work.