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General Tech Bugs & Fixes 2 years ago
Posted on 16 Aug 2022, this text provides information on Bugs & Fixes related to General Tech. Please note that while accuracy is prioritized, the data presented might not be entirely correct or up-to-date. This information is offered for general knowledge and informational purposes only, and should not be considered as a substitute for professional advice.
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Since Mathematica is contained in Raspberry Pi 2, I can do the following in the terminal:
echo "2+2" | /usr/local/bin/math -batchinput -batchoutput
It outputs 4 correctly. But when I try it with php:
4
php $math="echo '2+2' | /usr/local/bin/math -batchinput -batchoutput"; $handle = popen($math, "r"); $str=fread($handle,200); echo $str; ?>
It says that
Mathematica cannot find a valid password.
I find the license for Mathematica, in
/opt/Wolfram/WolframEngine/10.0/Configuration/Licensing/mathpass
Does this mean that Mathematica needs another license for interface with php?
UPDATE
I have solved this by adding an active key and password for the user www-data, which will stored in /var/www/.WolframEngine/Licensing/mathpass.
www-data
/var/www/.WolframEngine/Licensing/mathpass
Mathematica on the Raspberry Pi already comes with a license preinstalled, however running it as a user with insufficient access privileges may result in a prompt for activation or a password.
Here is a slightly more detailed explanation of what is happening, which is also discussed on Wolfram Community.
Early in the kernel (or FrontEnd) startup, as part of a series of hardware checks, Mathematica needs to talk to the Broadcom VideoCore chip. The default permissions for device should be similar to
crw-rw---- 1 root video 250, 0 Oct 27 22:17 /dev/vchiq
For example, if the user is not a member of the video group, opening the device will fail, resulting in a different $MachineID which no longer matches the preinstalled password. Hence, the product will not be activated.
video
$MachineID
A good way to resolve this issue is to check the device permissions are as above, and add the non-privileged user to the video group
sudo usermod -a -G video www-data
I have solved this by adding an active key and password for the user www-data
Yes, this will also work, but is more expensive: it requires the Pi owner (or his organization) to have purchased a Mathematica license. That is not necessary on the Raspberry Pi.
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