[Fsf-friends] Verification of program output

Ramanraj K ramanraj@md4.vsnl.net.in
Tue Dec 23 21:00:39 IST 2003


Chandrashekhar Mullaparthi wrote:

>Verifying the output is not practical for the average end user except for
>the most trivial piece of software.
>
A serious discussion on this would be very long :-)  However, we may 
briefly check on this, so that we may practically benefit out of this 
discussion.

So far as office suites and text editors are concerned, the output is 
fairly obvious and we can take back up of the files we create.  Even if 
the software fails, we can simply reinstall or use some other machine 
with our back up files and continue with our work.  We may also backup 
the contents of directories containing valuable files. The only 
verification we do in these cases, is check if the backup is written 
correctly.

I use PostgreSQL database server.  The backup for my database is done 
merely with:

# pg_dump dbname > dbdumpname

dbdumpname is a mere text file, that we could open with a text editor 
and read.  I could check on every thing: from the database schema to the 
contents of the table.  If it is a very large database, we can break up 
the output and share work among different users. In the case of a crash, 
I may use the backup merely with:

# dropdb dbname
# createdb dbname
# psql -e dbname < dbdumpname

Generally, every application worth its name maintains error logs that 
enable bug fixing and trouble shooting.  Some sort of feedback system 
should be available if not already there.

Practically, some kind of checking on the output directly with our 
senses, through the same machine or a different machine is generally 
possible.  My fair rent calculator script is more than 50K long but the 
ouput may be only 10 to 15 lines long, and the user may concern himself 
with just this, and not really worry about the 50K of source code. 
 PostgreSQL is a complex application I use, and the output can be 
reasonably verified, both while actually using and through backups.

Further, is not eternal vigil always desirable?  This is a must, if we 
desire to remain in control of our computers.








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