Use variables

CL procedures consist of CL commands, and the commands themselves consist of the command statement, parameters, and parameter values.

Parameter values may be expressed as variables, constants, or expressions. A variable is a named changeable value that can be accessed or changed by referring to its name. Variables can be used as substitutes for most parameter values on CL commands. When a CL variable is specified as a parameter value and the command containing it is run, the value of the variable is used as the parameter value. Every time the command is run, a different value can be substituted for the variable. Variables and expressions can be used as parameter values only in CL procedures and programs.

Variables are not stored in libraries; they are not objects; and their values are destroyed when the procedure that contains them is no longer active. The use of variables as values gives CL programming a special flexibility, because this allows high-level manipulation of objects whose content may change by specific applications. You might, for instance, write a CL procedure to direct the processing of other programs or the operation of several workstations without specifying which programs or workstations are to be controlled. The system identifies these as variables in the CL procedure. You can define (specify) the value of the variables when running the CL procedure.

In addition to the uses discussed in this section, variables can be used to:

Pass information between procedures and jobs.
Pass information between procedures and device displays.
Conditionally process commands.
Create objects. A variable can be used in place of an object name or library name, or both. The following example shows the Create Physical File (CRTPF) command used with a specified library in the first line, and with a variable replacing the library name in the second line:
```
CRTPF  FILE(DSTPRODLB/&FILE)
CRTPF  FILE(&LIB/&FILE)
```

Variables cannot be used to change a command name or keyword or to specify a procedure name for the CALLPRC command. Command parameters, however, can be changed during the processing of a CL procedure through the use of the prompting function.

It is also possible to assemble the keywords and parameters for a command and process it using the QCAPCMD API or QCMDEXC API.

Declare a variable
All variables must be declared (defined) to the CL procedure before they can be used by the procedure.
Use based variables
Based variables can be used to map variables passed to the program or manipulate arrays of values.
Use defined variables
Defined variables make it easy to manage complex data structures in CL by eliminating the need to substring values out of a large variable.
Specify a list or qualified name using a variable
Variables can be used to specify a list or qualified name.
Case of characters in variables
There are restrictions on the case used for characters in variables.
Variables replacing reserved or numeric parameter values
Character variables can be used for some commands to represent a value on the command parameter.
Change the value of a variable
You can change the value of a CL variable using the Change Variable (CHGVAR) command.
Trailing blanks on command parameters
This describes how trailing blanks are handled on command parameters.
Write comments in CL procedures
This describes how to write comments in CL procedures.

Parent topic: CL programming

Work with multiple device display files

Prompt for user input at runtime

QCAPCMD program

QCMDEXC program

Data type errors using the CALL command

Related reference

Control processing within a CL procedure