SUBSTRINGSTART Function

Returns the start location of the n captured sub-pattern.

Category:	Regular Expression
Requirement:	The regular expression must contain sub-patterns that can be used to match patterns.
Returned data type:	Integer

Table of Contents

Syntax

r.SUBSTRINGSTART(n)

Required Argument

n

specifies a positive integer that indicates the sub-pattern whose starting location you want to be returned.

Requirement	n must not be NULL or blank.

Details

The SUBSTRINGSTART function takes the input integer n that you supply and returns a starting location for the sub-pattern represented by that input integer. NULL is returned if there is no substring currently under consideration and therefore no location to return.

Use SUBSTRINGCOUNT( ) to determine the number of sub-patterns under consideration. Use SUBSTRINGLENGTH( ) with this function to pull out the matched sub-patterns and use them in evaluation logic of your expression code.

Most simple regular expressions will not have sub-patterns and this function will behave similarly to MATCHSTART(). However, if your regular expression does use sub-patterns, then this function can be used to find the starting point of individually captured sub-patterns found within the overall matched pattern.

Example

Note: This example can be run in a stand-alone expression node if the Generate rows when no parent is specified option is selected. If passing data to this node instead, turn this setting off and remove the SETEOF() function. The PUSHROW statements are also unnecessary if passing data values in to the node as data rows. Unless stated otherwise, all code shown should be entered in the Expression tab of the Expression node.

//Define some variables
string MyString
string MyString2
integer i
integer SSC
integer SSS
integer SSL
 
// Set initial values for variables
i = 0
SSS = 0
SSL = 0
SSC = 0
 
// Sample inpit string
MyString = "DataFlux Data Management Studio"
 
// Define a regular expression object
regex r
// Then compile it - notice the use of ( and )
r. compile("(DataFlux|DF) Data Management (Studio|Platform)")
// Find the first substring
if r.findfirst(MyString)
   begin
      // Use the "substring" functions to find the number of substrings
      SSC = r.substringcount()
      // Loop through substrings
      for i = 1 to SSC
      begin
      // Then pull out substrings
      SSS = r.substringstart(i)
      SSL = r.substringlength(i)
      MyString2 = mid(MyString,SSS,SSL)
      // Place the substrings in a data row
      pushrow()
      end
   end
// Terminate the expression node processing
seteof(true)
// Prevent the last pushrow() from showing up twice
return false

//Define some variables
string MyString
string MyString2
integer i
integer SSC
integer SSS
integer SSL
 
// Set initial values for variables
i = 0
SSS = 0
SSL = 0
SSC = 0
 
// Sample inpit string
MyString = "DataFlux Data Management Studio"
 
// Define a regular expression object
regex r
// Then compile it - notice the use of ( and )
r. compile("(DataFlux|DF) Data Management (Studio|Platform)")
// Find the first substring
if r.findfirst(MyString)
   begin
      // Use the "substring" functions to find the number of substrings
      SSC = r.substringcount()
      // Loop through substrings
      for i = 1 to SSC
      begin
      // Then pull out substrings
      SSS = r.substringstart(i)
      SSL = r.substringlength(i)
      MyString2 = mid(MyString,SSS,SSL)
      // Place the substrings in a data row
      pushrow()
      end
   end
// Terminate the expression node processing
seteof(true)
// Prevent the last pushrow() from showing up twice
return false

Last updated: May 7, 2024