What does Posix Compliance on my HP3000 do for me?

Posix Compliance on an MPE/iX machine gives you the reliability that you have come to expect from MPE for many years and at the same time allows you to reap the benefits of concepts widely used in other operating systems. In this article I will show you how to use a Posix concept known as Symbolic Links in the MPE/iX environment. (There are many Posix methods that you can apply directly to your system without the need to enter the Posix Shell and I will discuss more of them in future articles.)

A symbolic link is like a permanent file equation that goes much further. The existence of a symbolic link makes all references to a filename to automatically reference a different file including run, print, build, purge, fcopy, editor, dbopen… You can use symbolic links for databases, programs, command files, and directories. A symbolic link is created by issuing the MPE command :NEWLINK as in this example:

:newlink link=myfile;to=myfile2.temp

Now any command or program that references “myfile” will instead reference “myfile2.temp”. Other related commands that you need to know regarding symbolic links are:

: PURGELINK myfile  (to remove a symbolic link called myfile)
: LISTFILE  @. @. @ , 7 ;seleq=[object=symlink]  (to list all symbolic links on the system)

One application for symbolic links is a project that involves moving a database or a group of files to a different group and/or volume set. Changing the file names typically involves adjusting UDCs, command files, hundreds of batch jobs, and possibly recompiling programs. Creating a symbolic link one time for each file eliminates all of those changes and the problems that would undoubtedly occur.