Singular

I mean, if there is such a folder... I need to copy procedures created by my teacher and another student to cope with differential forms in a way that didn't exist before in Singular, so I need to copy the procedures, edit the lib files in some way... I need to add extra info to the standard libraries of Singular, but in Ubuntu Januty system. Does anyone know how to do it?

Hi,
like any part of an installed software, one should not change the installed libs in the system folders. (this might corrupt the software). But you could define alternative location for the changed libraries using environment variables.
See http://www.singular.uni-kl.de/Manual/3-0-4/sing_47.htm

Your request can be interpreted in two ways:
1) You have root-priviledges on the given ubuntu-system and face the task of
making these libraries as well as the modified system libraries accessible to
all users on the machine.
In this case, you may find the correct directory in the following way:
-start Singular
-enter the command system("SingularLib")
In this way you obtain the search path for the Singular libraries in the standard
unix path syntax, which allows you to find the correct directories on your system.

Please do not change any libraries from the standard distribution.
If changes are necessary, create a copy of the library with a slightly
modified name, make the changes there and make sure that the respective
new libraries written by your colleagues call the 'new' library. The change in
the name of the library should involve something more than just an exchange
of lower case letters by upper case ones, because all characters in the
library name are changed to lower case upon loading.

2) If you are a user on the machine and you simply want to use your colleagues'
libraries which rely on modified system libraries in your colleagues' home
directories, then you can either copy or link those libraries into the directory
from which you are calling Singular. Libraries in this directory have precedence
over libraries in the main system directory tree.

I hope one of the answers solves your problem.
Best regards,
Anne

Thanks a lot, Anne and Dreyer, for your advices. They will certainly help me a lot.