Asking Questions Through Electronic Mail

User questions submitted through electronic mail to

consult@ncsa.uiuc.edu

are answered by the Consulting Services staff. The vast majority of problems can be resolved using electronic mail.

How to Help

You can greatly speed up the process of isolating and correcting errors you encounter while using the NCSA high-performance machines by providing the following information:

your name, login (account number), and phone number
a complete description of the problem including traceback information if available and appropriate

After checking with Consulting Services staff, you may be asked to provide:

access to your program if you are encountering run-time errors. The most common delay in providing timely assistance is caused by the inability to access program source and input files so that NCSA can reproduce the problem. NOTE: Consultants do not have superuser access and are unable to read your files unless you explicitly grant permission.
a complete description of how to compile and run your program. Provide a makefile, if possible.
if you are getting incorrect results, include an example of the correct results. Remember that NCSA staff may not be familiar with your algorithms and techniques.

NOTE: You should make every attempt to reproduce your error in a short program. Isolating the section of your long program that is creating the problem(s) will give you better turn-around when you request assistance from the consultants.

Access to User Files

For smaller programs (fewer than 1,000 lines), you can send a copy of the file to the consultants by electronic mail.

For larger programs, you must ensure that permissions are set so that

all files are world readable
sll directories (starting at your home directory down to the directory that your code is in) are world readable and world executable

(Contact the Consulting Services staff if you have specific security concerns about making your files world readable.)

The UNIX command used to set permissions is chmod, which allows symbolic names for permission modification in addition to the octal numbers used by UNIX. To permit others to read your files, enter:

% chmod a+r filename

where a represents shorthand for the UNIX owner, group, and world permissions and filename is the name of the file you want others to examine. You can supply multiple filenames on the chmod command line.

You can let others read all the files in a directory by using a wildcard. For example, entering chmod a+r * causes all files in your current directory to be readable by others.

Granting read permissions for your files is usually not enough to allow the consultants to retrieve these files, however. You must still ensure that all directories in the path to the files in question are executable (and, preferably, readable as well). Below is an example of granting read and execute permission for the directory /scr1/u12345:

% chmod a+rx /scr1/u12345

A full description of the chmod command is available online by entering man chmod.

Remember to change permissions back once you have received help. Enter:

% chmod o-r *

to remove the world read permission for all the files in your current directory (o represents others). Or you can enter chmod og-r * to remove the world and group read permissions for all the files in your current directory.

Enter:

% chmod o-rx directory

to remove world read and execute permission from the directory called directory. Or you can enter chmod og-rx directory to remove the world and group read and execute permission from the directory.

Asking Questions via Email

How to Help

Access to User Files