HP 3000 Manuals HP 3000 Manuals
Obtaining Input
Input to a command file or UDC can be supplied through parameter
specifications entered when the command file or UDC is issued.
Interactive prompts and responses can be embedded in the command file to
receive input from the caller. Predefined command input can also be
retrieved from an input file.
Identifying Parameters
PARM statements can be inserted in a command file or UDC to define
parameter data that is entered when the command file or UDC is issued.
The following example shows the command input to invoke the FILINFO
command file. The file name A is provided when the command file name is
issued.
FILINFO A
If parameter data is desired, one or more PARM statements can be included
in the command file. For UDCs, parameters can be defined using the UDC
name line, PARM statements, or both. Each entry defines one or more
required or optional parameters. The following example defines the
parameter input, a file name, in a PARM statement. The subsequent FINFO
statement uses the parameter value to verify the existence of the named
file. Note that a parameter must be explicitly dereferenced in all
commands and expressions.
PARM FNAME
IF NOT (FINFO("!FNAME","EXISTS")) THEN
:
In this example, the file name is a required parameter since no default
value has been provided for the parameter field. In processing the
command file, the file name is inserted in any expression where the
parameter FNAME is dereferenced, such as in the FINFO statement.
NOTE Parameters must be accessed by explicit dereferencing. Implicit
dereferencing will result in either a message stating that the
variable does not exist or insertion of a variable value of the
same name.
Parameter data is optional if a default value is provided in the PARM
statement or UDC name line. The following example of the LIST command
file defines six parameters and supplies default values for five of them.
Note that the two PARM statements are used to differentiate between
required and optional parameters.
PARM F1
PARM F2=$NULL,F3=$NULL,F4=$NULL,F5=$NULL,F6=$NULL
This example allows up to six file names to be entered when the command
file is invoked. The first file name is the only required parameter.
The value $NULL is substituted as the default value for the optional
parameters. The following example shows how the LIST command file could
be invoked.
LIST A,B,C
Each of the three parameters is matched with its associated parameter
name. The file name A is identified as F1, the first parameter. File
name B is F2, and file name C is F3. Because no other parameters were
supplied in the call, F4, F5, and F6 contain the default value $NULL.
This method of coding is often used in looping constructs to provide
input to multiple iterations of a process with a single invocation.
In a UDC, parameter data can be specified in two ways. Parameters can be
defined in the UDC header on the line containing the UDC name, as shown
in the following example.
LIST F1,F2=$NULL,F3=$NULL,F4=$NULL,F5=$NULL,F6=$NULL
Parameters can also be entered on the line after the UDC name and
identified by the PARM keyword, as in command files.
LIST
PARM F1,F2=$NULL,F3=$NULL,F4=$NULL,F5=$NULL,F6=$NULL
Note that both of these methods can be used within a single UDC, as shown
in the following example.
LIST F1
PARM F2=$NULL,F3=$NULL
PARM F4=$NULL,F5=$NULL,F6=$NULL
Prompting for Input
The INPUT command prompts the user for input data and reads user input
from $STDIN, the user's terminal, into a defined variable. The data
received with the INPUT command is considered string, even if it consists
of numeric data.
The INPUT command allows three parameters. The first parameter specifies
the variable name for the input data. The second specifies a character
string to be used as the prompt. The length of time allowed for the user
to enter input data can be specified by entering a third parameter.
In the following example, the echoed statements and the prompt for the
user's selection create a menu of run variations. The user's selection
at the prompt triggers a branch to the appropriate routine.
ECHO Enter 0 to exit.
ECHO 1 to review database.
ECHO 2 to update database.
INPUT CHOICE,"Which number do you select?",15
In the preceding example, the options in the ECHO commands and the
prompting phrase from the INPUT command are displayed at the user's
terminal. The variable, CHOICE, receives the user's response, to be
analyzed in later processing. Fifteen seconds (,15) specifies the length
of time to wait for a reply.
Retrieving Input from a File
By using redirection indicators, most CI statements can retrieve input
from a file rather than from parameter data or direct user input. The
name of the file containing the input data is preceded by the redirection
indicator for input (<) and added to the appropriate statement. Only a
single file name can be specified for input redirection; wildcard
characters, therefore, cause errors. The following example shows how the
editor is invoked and its input file specified in a single statement.
:EDITOR <INSFILE
When input is redirected, the file must exist. Unless otherwise
specified in a file equation, the CI searches for a TEMP file first, then
a permanent file. By default, it opens the file for read and share
access. These defaults can be overridden by using a backreference to a
file equation.
Redirection supports HFS (hierarchical file system) names. ECHO Hi
There! >> ./somefile appends to the file ./somefile
The following example receives processing input by redirecting the INPUT
command's source from the user's terminal to a file named INFILE. The
first record of INFILE is read into the variable named RECORD.
INPUT RECORD <INFILE
Because of possible confusion with the less than (<) character,
redirection cannot be performed with the IF, WHILE, CALC, SETVAR, REMOTE,
or COMMENT statements. All other CI statements can perform input
redirection.