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strtok() woes.... How to separate out when two delims are right next to each other?

Posted on 2009-05-07
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Last Modified: 2012-05-06
Hi all,

I am having problems with strtok(). What I want is to get back an empty char when two delims are right next to each other. See my code for example..

I want:
paramPointers[0] = "toaster"
paramPointers[1] = "oven"
paramPointers[2] = "sink"
paramPointers[3] = ""
paramPointers[4] = ""
paramPointers[5] = "television"
paramPointers[6] = "stove"
paramPointers[7] = "fridge"

but what I am getting is:

paramPointers[0] = "toaster"
paramPointers[1] = "oven"
paramPointers[2] = "sink"
paramPointers[3] = "television"
paramPointers[4] = "stove"
paramPointers[5] = "fridge"
paramPointers[6] = nil
paramPointers[7] = nil
char delims[5] = "";
	strcpy(delims, "|");
 
	strcpy(receiveResponse, "toaster|oven|sink|||television|stove|fridge");
	
	receiveTok = strtok(receiveResponse, delims);
	
	while(receiveTok != NULL && iToken < MAX_PARAMS)
	{
		paramPointers[iToken] = receiveTok;
		
		iToken++;
		receiveTok = strtok (NULL, delims);
	}

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Question by:ehensens
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8 Comments
 
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Expert Comment

by:Infinity08
ID: 24326164
strtok already treats multiple separator characters as one. So, I'm not sure what the question is.
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Accepted Solution

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evilrix earned 1000 total points
ID: 24326165
If you read the description for how strtok works I think you'll see why this isn't doing what you want.

"To determine the beginning and the end of a token, the function first scans from the starting location for the first character not contained in delimiters (which becomes the beginning of the token). And then scans starting from this beginning of the token for the first character contained in delimiters, which becomes the end of the token."

http://www.cplusplus.com/reference/clibrary/cstring/strtok/
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Author Comment

by:ehensens
ID: 24326193
Hi evilrix,

So are you confirming that my code as is will not do what I want, just by the nature of strtok(), i.e. "||" will always be seen as "|"?
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LVL 53

Assisted Solution

by:Infinity08
Infinity08 earned 1000 total points
ID: 24326217
Ah, sorry, you DON'T want it to treat multiple separators as one.

Then you can't use strok :) You'll have to write your own tokenizer for that.
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LVL 40

Expert Comment

by:evilrix
ID: 24326242
Try this, it should do what you are looking to do with strtok.
#include <string>
#include <vector>
#include <sstream>
 
#define MAX_PARAMS 25
 
int main()
{
	std::string receiveResponse = "toaster|oven|sink|||television|stove|fridge";
	std::vector<std::string> params;
 
	std::stringstream ss(receiveResponse);
	std::string s;
 
	while(std::getline(ss, s, '|'))
	{
		params.push_back(s);
	}
}

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Expert Comment

by:evilrix
ID: 24326263
^^^ I say should because I didn't test it very well :)
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Author Comment

by:ehensens
ID: 24326325
So, then how would I get from params to a type:

    char* parameters[MAX_PARAMS];


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LVL 40

Expert Comment

by:evilrix
ID: 24326460
You don't... you use vector. There is no need to use the unsafe fixed array construct in C++.
http://www.cplusplus.com/reference/stl/vector/

If you need something that can be used in place of char* parameters[MAX_PARAMS]; you can use

char* parameters = &params[0];

However, please note this is only valid as long as no mutating functions (non-const) are called on vector and you do NOT delete[] on this pointer as it is managed by vector.
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