Are you creating commands to improve your productivity?

This article is the first of several related to creating your own user CL commands. We will start with a simple command definition and then enhance the command with various features in order to demonstrate how to incorporate these extensions within your own commands. But first we need a command scenario.

In a CL program, have you ever wanted to concatenate a decimal value to a character string and then display the result? That is, take a character string such as 'The cost is $', append a decimal value such as 1.23, and then display a result of "The cost is $1.23" as attempted in the following program?

Pgm                                                         

Dcl        Var(&Number)   Type(*Dec)  Len(6 2)  Value(1.23)  

SndPgmMsg  Msg('The cost is $' *Cat &Number)                 

EndPgm

If so, you found out quickly enough that the *Cat built-in (along with *BCat and *TCat) does not support the concatenation of character and decimal operands. Suppose you attempt to compile the previous source as program SAMPLE using the following command:

CRTBNDCL PGM(SAMPLE)

This will result in the compile failures CPD0712 – Operand does not have valid type for operator, and CPD0711 – Operands in expression not same type. The CL concatenation built-ins only support character strings. Adding an intermediate character conversion, as shown below with the &Char variable, gets you close, but not quite to the desired result.

Pgm                                                        

Dcl        Var(&Number)   Type(*Dec)  Len(6 2)  Value(1.23)  

Dcl        Var(&Char)     Type(*Char) Len(10)                 

ChgVar     Var(&Char) Value(&Number)                       

SndPgmMsg  Msg('The cost is $' *Cat &Char)                 

EndPgm

Rather than "The cost is $1.23", you have "The cost is $0000001.23". This is due to the CHGVAR command, as documented, right-justifying the resulting character value of &Number and padding on the left with zeros. For some, this might be good enough; for others, the leading zeroes in the resulting message will just not be acceptable. To remove the leading zeroes and left-justify the value of the &Char variable, you might then change the program as shown below.

Pgm                                                             

Dcl        Var(&Number)   Type(*Dec)  Len(6 2)  Value(1.23)     

Dcl        Var(&Char)     Type(*Char) Len(10)                   

Dcl        Var(&Char_Siz) Type(*UInt) Value(10)                 

Dcl        Var(&Char_Pos) Type(*UInt)                            

Dcl        Var(&Char_Rem) Type(*UInt)                            

ChgVar     Var(&Char) Value(&Number)                            

DoFor      Var(&Char_Pos) From(1) To(&Char_Siz)             

           If Cond(%sst(&Char &Char_Pos 1) *EQ '0') +       

              Then(Iterate)                                 

           Else Cmd(Leave)                                  

           EndDo                                            

ChgVar Var(&Char_Rem) Value((&Char_Siz + 1) - &Char_Pos)      

ChgVar Var(&Char) Value(%sst(&Char &Char_Pos &Char_Rem))  

SndPgmMsg  Msg('The cost is $' *Cat &Char)                  

EndPgm                                                       

The IF test within the DOFOR is checking for leading zeros within the &Char variable by examining each single byte character of the &Char variable one character at a time. Variable &Char_Pos identifies the character currently being examined and is the VAR control variable for the DOFOR loop. If a leading zero is found, the routine uses the ITERATE command to move to the next character of the &Char variable. When a non-zero character is encountered, the LEAVE command is run and the DOFOR is exited.

When the DOFOR loop is exited, the program left-adjusts all remaining characters of the &Char variable, starting with the first non-zero character found, and then blank pads any remaining positions of the &Char variable. To do this, the variable &Char_Rem is used to represent the number of significant characters REMaining in the &Char variable after trimming any leading zeros. Upon setting the correct value of &Char_Rem, the CHGVAR command (with a keyword VAR value of the full variable name &Char and a keyword VALUE parameter value defining the relevant substring of &Char) is used to left-adjust the significant characters of &Char and blank pad any positions of &Char beyond the %sst specified length.

Because CL variable &Number is declared with two decimal positions, the IF test will always find a non-zero value— the decimal point if nothing else. Note, though, that handling negative values for the &Number variable will require an additional check if we want to trim leading zeros, as the negative sign precedes the leading zeros when returned from the initial CHGVAR command. This check for negative values will be handled in a subsequent article. Compiling and running the sample program using a range of &Number values, the program displays the following messages for various non-negative &Number values.

&Number          Message displayed

0                The cost is $.00

1.23             The cost is $1.23

1234.56          The cost is $1234.56

This is much better! It's also likely that this logic, left-adjusting and removing leading zeros, can be useful to many other CL programs. To share this logic, you could copy this DOFOR routine to the other programs or make it into a subroutine and use the CL INCLUDE command to include the logic into multiple programs, but you will most likely need to tweak this code (or the other programs) as the CL character variable is unlikely to be called &Char in all of these other programs. A better approach might be to create a user command that implements this logic.

Before going any further, I will point out that actually a "better" solution, for this specific scenario, might be to utilize the message-handling support of the i operating system in formatting the value of the &Number variable:

1. Create a message file (or use an existing message file) with this command:

CrtMsgF MsgF(MyLib/MyMsgs)

2. Add a message description with a message replacement variable definition based on the CL &Number variable:

AddMsgD MsgID(MSG0001) MsgF(MyLib/MyMsgs) +

Msg('The cost is $&1') Fmt((*Dec 6 2))

3. Send this message as shown below:

Pgm                                                          

Dcl        Var(&Number) Type(*Dec)  Len(6 2)  Value(1.23)    

Dcl        Var(&Char)   Type(*Char) Len(4) +                 

Stg(*Defined) DefVar(&Number)                   

SndPgmMsg  MsgId(MSG0001) MsgF(MyLib/MyMsgs) MsgDta(&Char)   

EndPgm 

But as this article is intended to introduce you to the topic of creating your own highly flexible user commands, we'll bypass using the message-handler approach. Our command will be named Trim Left Characters, or TRMLFTCHR. The command definition is shown below.

Cmd        Prompt('Trim Left Characters')              

Parm       Kwd(Var) Type(*Char) Len(10) RtnVal(*Yes) + 

             Min(1) Prompt('Decimal value')                   

The TRMLFTCHR command defines one parameter, VAR. VAR is defined as a character variable with a length of 10 bytes and has a prompt display of "Decimal value". Because of the RTNVAL(*YES) specification on the PARM command, the TRMLFTCHR command can return an updated value using the VAR parameter. The MIN(1) specification indicates that the VAR parameter is required. To create the TRMLFTCHR command, you use the following Create Command (CRTCMD) command.

CRTCMD CMD(TRMLFTCHR) PGM(TRMLFTCHR) ALLOW(*IPGM *BPGM *IMOD *BMOD)

The CMD parameter of the CRTCMD command specifies the name of the command being created—TRMLFTCHR. The PGM parameter identifies the name of the command processing program (CPP) —in this case, also TRMLFTCHR. The ALLOW parameter specifies where the command can be run. The values shown indicate that the command can only be run in a CL program (ILE or OPM) or a CL ILE module (bound into a program). The TRMLFTCHR command cannot be run interactively (from, for instance, the command line) as the user of the TRMLFTCHR command must specify a CL variable name for the VAR parameter in order to receive the updated value. And a CL variable name is only possible within a program or module.

If your system is at V6R1 or later, you can specify the ALLOW parameter on the CMD statement of the command definition. Changing the CMD statement as shown below avoids the need to remember to re-specify the ALLOW parameter every time you need to recreate the command.

Cmd        Prompt('Trim Left Characters') ALLOW(*IPGM *BPGM *IMOD *BMOD)

The CPP, TRMLFTCHR, is shown below.

Pgm        Parm(&Char)                                        

Dcl        Var(&Char)      Type(*Char) Len(10)                

Dcl        Var(&Char_Siz)  Type(*Uint) Value(10)              

Dcl        Var(&Char_Pos)  Type(*UInt)                        

Dcl        Var(&Char_Rem)  Type(*UInt)                        

DoFor      Var(&Char_Pos) From(1) To(&Char_Siz)               

           If Cond(%sst(&Char &Char_Pos 1) *EQ '0') +         

              Then(Iterate)                                   

           Else Cmd(Leave)                                    

           EndDo                                              

If         Cond(&Char_Pos *LE &Char_Siz) Then(Do)             

           ChgVar Var(&Char_Rem) +                            

                    Value((&Char_Siz + 1) - &Char_Pos)        

           ChgVar Var(&Char) +                               

                    Value(%sst(&Char &Char_Pos &Char_Rem))   

           EndDo                                              

Else       ChgVar Var(&Char) Value('0')                      

EndPgm                                                       

As you can see, the CPP is essentially the logic we previously added to the application program. The two additions are defining the &Char variable as a parameter to the program (representing the VAR parameter of the TRMLFTCHR command) and an IF test upon exiting the DOFOR loop.

The new IF test is to cover the situation where there is no decimal point in the &Char value being processed and the value passed is all zeros. With the previous sample program, this will never occur as &Number is defined with two decimal positions and the initial CHGVAR command will return a character value of .00 for a &Number value of 0. However, other programs using the TRMLFTCHR command may be using a decimal variable declared with zero decimal positions—in which case, a numeric value of 0 will be represented by the character string "0000000000"—causing the CPP to iterate through the entire character string.

If all zeros are found in &Char, the DOFOR loop will exit with a &Char_Pos value greater than &Char_Siz (as &Char_Size is the DOFOR control variable specified with the TO keyword) or, to look at it another way, the value of &Char_Pos will be less than or equal to &Char_Siz if a non-zero value is encountered in the DOFOR loop and the LEAVE command is run. If a non-zero character is found, the same logic is applied as in the sample program: left-adjust and blank pad the significant characters of the &Char parameter. If only zero characters are found (the ELSE logic added to the CPP), the &Char variable is set to the single character value of '0' and then blank padded.

To create the TRMLFTCHR CL program use either of the following commands.

CRTBNDCL PGM(TRMLFTCHR)

or

CRTCLPGM PGM(TRMLFTCHR)

Returning to the earlier sample application program, we can now replace the logic associated with removing leading zeros and left-adjusting the result with the TRMLFTCHR command as shown below.

Pgm                                                         

Dcl        Var(&Number)   Type(*Dec)  Len(6 2)  Value(1.23) 

Dcl        Var(&Char)     Type(*Char) Len(10)                

ChgVar     Var(&Char) Value(&Number)                        

TrmLftChr  Var(&Char)

SndPgmMsg  Msg('The cost is $' *Cat &Char)                  

EndPgm

This program, when run, will now display the message:

The cost is $1.23   

Any CL program needing to similarly display a character variable representing a numeric value can now use the TRMLFTCHR command—using the character variable name currently in use by the program for the VAR parameter and using any decimal variable value that can be represented in a 10-byte character variable. Not too bad. And certainly easily re-useable code by way of creating our own command.

There are, however, some limitations and considerations to the TRMLFTCHR command. One limitation is that it only supports 10-byte character variables for the VAR parameter. To verify this, change the definition of &Char in the sample application program from 10 bytes to 9. You will find that the compile fails with CPD0784 – Variable &CHAR for parameter VAR must be *CHAR, minimum length 10. Changing the definition of &Char in the sample program from 10 bytes to 11 will not result in a compile failure, but running the sample program may also not show the message you were expecting. This unexpected result will occur if the eleventh byte of the larger VAR variable is not a blank. As only the first 10 bytes of the VAR variable are being processed by the command, any value in the eleventh byte will not be left-adjusted or used while blank padding.

In the next article, we'll look at what's required to support a VAR CL character variable of virtually any length (and, in the third article of this series, we'll remove the qualifier "virtually").

More CL Questions?

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