HP 3000 Manuals HP 3000 Manuals
Starting Programs
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|The documentation that accompanies each program explains what it does |
|and how to use it. In particular, the use of HP Easytime/iX is |
|presented in detail in chapters 1, 2, 3, and 4 of Using Your |
|System. |
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You have three ways of starting--sometimes called running--any program on
your MPE/iX system.
* starting a program with the RUN command
* starting a program without the RUN command
* starting a program with the XEQ command
It might seem odd to have three ways of starting (running) a program. On
earlier MPE systems, the only way to start a program was to use the RUN
command. As the system evolved, programming engineers added other
methods, to provide more flexibility and to manage the growing complexity
of the system and its facilities.
Which method you use is usually a matter of choice. However, under some
circumstances, one method will work, and another will not.
Starting with the RUN command
RUN is one of the commands built into the MPE/iX operating system. Its
chief purpose--but not the only one--is to start a program.
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|You may use the RUN command to start any program that exists on your |
|system--provided that the program is not restricted from general use |
|by some method of protection. |
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Consider a program called AUDIT that resides in the REPORTS group of the
FINANCE account. Its fully qualified name is AUDIT.REPORTS.FINANCE.
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|Notice that programs are files, too. They have fully qualified names:|
|AUDIT.REPORTS.FINANCE. |
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Wherever you log on, you can run AUDIT this way:
RUN AUDIT.REPORTS.FINANCEReturn
This way of starting a program works for any program, if you know the
fully qualified name of the program file, and if the program is not
restricted from general use by some method of protection.
Notice, though, that
RUN AUDITReturn
will not work, unless you are logged on in the group where the AUDIT
program is found (in the REPORTS group of the FINANCE account in this
example).
Starting without the RUN command
However, if you are logged on as JOHN.FINANCE,REPORTS, you can run AUDIT
this way:
AUDITReturn
This "first name only" way of running a program is called an implied RUN.
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|This second method of running a program may not work in each and every|
|case. |
| |
|Before the computer can start a program, it must first find the |
|program on the disk. Using RUN with the fully qualified name of |
|the program tells the computer specifically where to find that |
|program. |
| |
|Using an implied RUN forces the computer to search for the program. |
|To do that, it follows a search path |
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![[]](../../pic3k/M011763/FFN423c50.gif)
Figure 4-2. Default Search Path
Path restriction.
If you use an implied RUN (AUDITReturn), the computer follows a set of
instructions called a path. These instructions tell the computer where
to search for programs (or any executable file). If the program resides
in an account (or in a group) not mentioned in the path instructions, the
computer will not find that program.
By default the path instruction tells the computer to search in these
places, in this order:
1. the group in which you are currently logged on
2. the PUB group of the account in which you are currently logged on
3. the PUB group of the SYS account
You can discover what path is set for you by entering this:
SHOWVAR HPPATHReturn
HPPATH is a system variable (an area of computer memory) that contains
the path instruction. The SHOWVAR command displays the setting of
this--or any other--system variable. SHOWVAR @Return will display the
settings of all of the system variables for your session.
The SETVAR command allows you to change the path along which the computer
searches for executable files. You may use the SETVAR command to change
the value of a system-defined variable called HPPATH.
If the program that you want to run is not found along the path
instructions, you will need to use RUN and specify the fully qualified
name of the program.
Name restriction.
Still another limitation on using an implied RUN name might be the very
name of the program you want to run.
The computer follows a set of priorities--a search priority--in its hunt
for executable files. The priority of the search, from highest to
lowest, is this:
* highest priority: user-defined commands (UDCs)
* next priority: built-in commands (see Chapter 7 )
* lowest priority: programs and command files (see Chapter 8 )
User-defined commands are somewhat like command files, but they are an
advanced topic in using the MPE/iX operating system. You will find
information about user-defined commands in Using the 900 Series HP
3000:Advanced Skills (32650-60039). You may order this book through your
Hewlett-Packard representative. Other books that might be of interest
are mentioned in the Bibliography found in Chapter 8 of Using Your
System.
![[]](../../pic3k/M011763/FFN433c50.gif)
Figure 4-3. Search Priority
A program called MYPROG will come into conflict if there is a
user-defined command called MYPROG or if there is a built-in command
called MYPROG (there is no such built-in command, by the way).
1. If the computer finds a user-defined command called MYPROG, the
computer will execute that first and stop its search.
2. If, instead, the computer finds a built-in command called MYPROG,
the computer will execute that first and stop its search.
Only after it has exhausted these possibilities will the computer
continue its search for the program called MYPROG.
One of the MPE/iX built-in commands is called SHOWME. If there is also a
program called SHOWME on your system, you will encounter difficulty in
trying to run the program SHOWME. If you enter SHOWMEReturn, the
operating system will execute the command SHOWME and fail to execute the
program called SHOWME.
There are two solutions to this problem.
* One solution is to use the RUN command with the fully qualified
name of the program (RUN SHOWME.group.account).
* The other solution is to use the XEQ command.
Starting with the XEQ command
If you wish to execute a program called SHOWME and not the command called
SHOWME, you may use another command, XEQ, to execute the program SHOWME:
XEQ SHOWMEReturn
XEQ is a shorthand way of writing the English word "execute," and it has
other applications that are discussed in Chapter 6 . The XEQ command
bypasses the user-defined commands and the built-in commands before
searching for an executable file.