Displaying a Substring of a Character String Variable

The ILE source debugger does not support the reference modification syntax of ILE COBOL. Instead, you can use the %SUBSTR operator with the EVAL command to display a substring of a character string variable. The %SUBSTR operator obtains the substring of a character string variable from a starting element position for some number of elements.

Note: The ILE source debugger does not support COBOL's reference modification syntax for handling substrings. You need to use the %SUBSTR operator of the ILE source debugger to handle substrings.

The syntax for the %SUBSTR operator is as follows:

     %SUBSTR(identifier start-element number-of-elements)

where identifier must be a character string variable, and start-element and number-of-elements must be non-zero, positive integer literals. identifier can be a qualified, subscripted, or indexed variable. start-element + number-of-elements - 1 cannot be greater than the total number of elements in identifier.

For example, you can obtain the first 10 elements of a 20-element character string by using %SUBSTR(char20 1 10). You can obtain the last 5 elements of a 8-element character string by using %SUBSTR(char8 4 5). In the case of a DBCS or DBCS-edited item, element refers to a DBCS character (in other words, a two-byte character).

You can use the %SUBSTR operator to assign a substring of a character string variable to another variable or substring of a variable. Data is copied from the source variable to the target variable from left to right. When the source or target variables or both are substrings, then the operand is the substring portion of the character string variable, not the entire character string variable. When the source and target variable are of different sizes, then the following truncation and padding rules apply:

If the length of the source variable is greater than the length of the target variable, the character string is truncated to the length of the target variable.
If the length of the source variable is less than the length of the target variable, the character string is left justified in the target variable and the remaining positions are filled with blanks.
If the length of the source variable is equal to the length of the target variable, the two variables will be exact copies of one another after the assignment.

Note: It is possible to use a substring of the same character string variable in both the source variable and the target variable; however, if any portion of the target string overlaps the source string, an error will result.

Figure 1 shows some example of how the %SUBSTR operator can be used.

Figure 1. Displaying a Substring using the Debug %SUBSTR operator

                                Evaluate Expression
 Previous Debug expressions
 > EVAL CHAR10
    CHAR10 = '10CHARLONG'
 > EVAL CHARA
    CHARA = 'A'
 > EVAL CHARA = %SUBSTR(CHAR10 3 5)
    CHARA = 'C'
 > EVAL %SUBSTR(CHAR10 1 2) = 'A'
    CHAR10 = 'A CHARLONG'
 > EVAL %SUBSTR(CHAR10 1 2) = 'XYZ'
    CHAR10 = 'XYCHARLONG'
 > EVAL %SUBSTR(CHAR10 7 4) = 'ABCD'
    CHAR10 = 'XYCHARABCD'
 > EVAL %SUBSTR(CHAR10 1 2) = %SUBSTR(CHAR10 7 4)
    CHAR10 = 'ABCHARABCD'
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