Getting a string

This is a discussion on Getting a string within the C++ Programming forums, part of the General Programming Boards category; Hi, So, basically I want to extract a sequence of characters (which is located between two other sequences that I've ...

  1. #1
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    Getting a string

    Hi,

    So, basically I want to extract a sequence of characters (which is located between two other sequences that I've given) from a string.

    Code:
    char* str="abcdefghi";
    someFunction(str, "abc", "ghi"); 
    //this is the function that would do what I want. It would return "def"- the sequence that is located between the given strings. It's not necessary for it to be one function, it could be any technique that accomplishes what I want.
    Thank you.

  2. #2
    Kernel hacker
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    Look at functions like "strstr".

    Edit: I just realized that this is in the C++ section, in which case, perhaps you'd like to use the string class instead of char* for your string. In that case, functions find() and substr() are what you're looking for.

    --
    Mats

  3. #3
    C++ Witch laserlight's Avatar
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    I too would recommend using std::string with find() and substr(). However, how would you handle say, "abcdefghighi"? If you have a greedy matching, then the string in between the two others would be "defghi". For such a case, you might use rfind() instead of find().
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  4. #4
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    strstr() gives me the address of a substring in memory. How do I get the substring's location relative to the whole string?

    EDIT

    I'll try to use the C++ variant if I won't find a way to do it C-style.

  5. #5
    Sweet
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    Here is an example of a std::string function that finds a string between strings

    Code:
    #include <iostream>
    #include <string>
    
    std::string StringBetween(const std::string &findString, const std::string startString, const std::string endString)
    {
    	//Grab the length of the first string for moving the index
    	size_t startLength = startString.length();
    	size_t endLength = endString.length();
    
    	//Sanity Check: Cannot find between empty strings
    	if(0 == startLength || 0 == endLength){
    		return "";
    	}//if
    
    	//Find the index of the first string
    	size_t startIndex = findString.find(startString);
    
    	//If we can't find that string return blank
    	if(std::string::npos == startIndex){
    		return "";
    	}//if
    
    	//Increment the start index to get the contents between
    	startIndex = startIndex + startLength;
    
    	//Find the index of the end string
    	size_t endIndex = findString.find(endString, startIndex);
    
    	//If we can't find it return blank
    	if(std::string::npos == endIndex){
    		return "";
    	}//if
    
    	//We found our string within our indexes return it back
    	return findString.substr(startIndex, endIndex - startIndex);
    }
    
    int main()
    {
    	//The string to search between
    	std::string findString = "abcdefghi";
    
    	//The string that will contain the items between strings
    	std::string subString = StringBetween(findString, "abc", "ghi");
    
    	//Output the result
    	std::cout<<subString;
    
    	//"Wait" for input
    	std::cin.get();
    }

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