Algebra Filter Error

Algebra Filter Error

by Reza Khv -
Number of replies: 2
Can you help me?

When I write a statement (algebra) I receive: (I've actived the algebra filter)
Warning: escapeshellarg() has been disabled for security reasons in .../course/filter/algebra/filter.php on line 170

Warning: shell_exec() has been disabled for security reasons in .../course/filter/algebra/filter.php on line 173

Best,
Reza

Average of ratings: -
In reply to Reza Khv

Re: Algebra Filter Error

by Gregory Gorny -
Hi. its probably because linux is cutting off algebra and tex pics. I've got the same problem and unfortunately i don't know what to do about it. Now I'm only sure its the linux fault...
In reply to Gregory Gorny

Re: Algebra Filter Error

by John Forkosh -
I don't know for sure, but that error message doesn't sound to me like the image is being "cut off". Rather, it sounds like the argument containing the TeX expression that's supposed to be imaged is being cut off. And, without your TeX expression, mimetex can't render the desired image.

You can test this out using the public mimetex web server at http://www.forkosh.com/mimetex.cgi as follows. Suppose you want to enter the TeX expression $$$y=x^3$$$ and, therefore, to see the image mimetex.cgi?y=x^3. Then, where you would have written $$$y=x^3$$$, write instead the rather long and cryptic string
<img src="http://www.forkosh.com/mimetex.cgi?y=x^3" align=middle>
And, obviously, you can substitute any other TeX expression for y=x^3, to see any other image you want. And, if you do see an image using the img tag illustrated above, then images themselves aren't being cut off.

This public mimetex web service can also be used, exactly as described above, as a work-around for any Windows Server installation problem (or for any other installation problem). You can just write that img tag wherever you want, without installing mimetex or any moodle filter whatsoever, and without installing anything on your client machines, either. You need absolutely no software at all. Zero. Just write the img tag and it'll work.

The one inconvenience is writing that long img tag. Obviously, it's easier to write
$$$y=x^3$$$
than it is to write
<img src="http://www.forkosh.com/mimetex.cgi?y=x^3" align=middle>
every time you want to see y=x^3 (or any other TeX expression). The solution is a few lines of Perl in the moodle code to trap $$$...$$$ expressions and to rewrite them as the corresponding img tags, like I illustrated. If you do this, then you'll be able to use TeX expressions without installing any software whatsoever -- no server software and no client software. That should solve all your installation problems completely.

The one remaining glitch is that Zig's @@@...@@@ algebra filter can't be handled this way. You'll still need to install all Zig's software to use the algebra filter. But the $$$...$$$ TeX filter will be totally software-free.

Hope this helps with all the installation problems I've seen discussed in other threads.