C$REGEXP

Usage

CALL "C$REGEXP" 
    USING OP-CODE, parameters
    GIVING return-value

Parameters

Parameters vary depending on the operation selected. They provide information and hold results.

return-value: Numeric data item.

Unless otherwise noted, each operation returns a value or a status in return-value. Its contents vary by operation and the result of the operation.

Description

This routine allows you to use a regular expression to search a text string.

A regular expression is a formula for matching strings that have a certain pattern. For a complete description of regular expressions, see the POSIX 1003.2 standard appropriate for your platform. Windows platforms use the CAtlRegExp library; UNIX platforms use the POSIX C routines native to the platform.

A simple use of C$REGEXP is outlined in the following steps.

1. Use the AREGEXP-GET-LEVEL op-code to validate that the host platform provides support for regular expressions.
2. Validate and compile your regular expression with op-code AREGEXP-COMPILE. Your program should include an error handling routine in the event that the compiler finds an error in the expression.
3. Use op-code AREGEXP-MATCH to apply a compiled regular expression to a string to search for a match. You may want to do this iteratively to find all matches in the string.
4. Use op-codes AREGEXP-NUMGROUPS and AREGEXP-GETMATCH to work with subexpression matches.
5. Manage the memory used by this routine with op-codes AREGEXP-RELEASE-MATCH and AREGEXP-RELEASE.

Op-codes and Parameters

AREGEXP-GET-LEVEL (op-code 1)

This operation indicates whether regular expression support is available on the host. Its usage is:

CALL "C$REGEXP" USING AREGEXP-GET-LEVEL GIVING return-value

The value of return-value can be one of the following (defined in acucobol.def):

AREGEXP-COMPILE (op-code 2)

This operation compiles a regular expression to ensure that it has a valid form, returning a handle to the compiled regular expression or NULL if there is an error. Its usage is:

CALL "C$REGEXP" USING AREGEXP-COMPILE, reg-expr, flags
                GIVING return-value

reg-expr

Must be a NULL-terminated regular expression. It must be NULL-terminated because trailing spaces are allowed in regular.

flags

(Optional) is the sum of one or more of the following values (defined in acucobol.def):

return-value contains a handle to the compiled expression, or NULL if an error occurred.

AREGEXP-MATCH (op-code 3)

This operation applies a regular expression to a string, and returns a handle. The match-start parameter must be initialized before AREGEXP-MATCH is attempted, as it specifies the start position in which matching should begin. To see if there is a match you need to check match-start; If it is 0, there is no match. Its usage is:

CALL "C$REGEXP" USING AREGEXP-MATCH,
   reg-expr-handle, string, length, match-start, match-end
   GIVING return-value

AREGEXP-RELEASE-MATCH (op-code 4)

This operation frees memory that is allocated when AREGEXP-MATCH is called. Return-value is not used. Its usage is:

CALL "C$REGEXP" USING AREGEXP-RELEASE-MATCH match-handle

AREGEXP-RELEASE (op-code 5)

This operation frees the memory allocated when AREGEXP-COMPILE is called. Return-value is not used. Its usage is:

CALL "C$REGEXP" USING AREGEXP-RELEASE reg-expr-handle

AREGEXP-NUMGROUPS (op-code 6)

This operation returns the number of substrings that matched any subgroups in the regular expression. Its usage is:

CALL "C$REGEXP" USING AREGEXP-NUMGROUPS match-handle
                GIVING return-value

Depending on the construction of a regular expression, it is possible for a subgroup of the regular expression to match multiple substrings. This operation reports the number of instances found in the last AREGEXP-MATCH operation. For more information, rules, and examples, see the POSIX 1003.2 documentation or one of the many books available on regular expressions.

AREGEXP-GETMATCH (op-code 7)

This operation returns a set of indices into a string passed to AREGEXP-MATCH that match the subexpression of the regular expression. Its usage is:

CALL "C$REGEXP" 
    USING AREGEXP-GETMATCH, match-handle, group, 
    idx-start, idx-end
    GIVING return-value

The parameters are defined as follows:

AREGEXP-LAST-ERROR (op-code 20)

This operation returns the last error code returned by a call to C$REGEXP. Its usage is:

CALL "C$REGEXP" USING AREGEXP-LAST-ERROR GIVING return-value

The error value is returned in return-value. The possible error values (described in acucobol.def) have the following meanings: