Tokenizing Command Line Arguments

This is a discussion on Tokenizing Command Line Arguments within the C Programming forums, part of the General Programming Boards category; Hi, I am working on a tokenizer for command line arguments, to eventually work in a mini shell program. I ...

  1. #1
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    Question Tokenizing Command Line Arguments

    Hi,

    I am working on a tokenizer for command line arguments, to eventually work in a mini shell program. I cannot use strtok, I must get the arguments by hand. I have to ignore tokens that are in quotation marks.

    For example:
    cd ls "test"

    token 0 - cd
    token 1 - is
    token 2 - "test"

    So I was thinking that if I had a pair of starting quotes, then I would advance the i counter until i hit the pair of ending quotes, then put that info into the token. Here is what I have that is definitely not working. Any ideas on what direction I am going, or not going in? Any guidance would be appreciated. Thanks.

    Code:
    struct token* tokenizer(char* __commandline,int* __argumentcounter)
    {
      /*the following data structure should hold all the tokens*/
      struct token* tokenlist = malloc(sizeof(struct token));
    
    		int i = 0;
    		int j = 0;
    		/*struct token* head = tokenlist;*/
    		struct token tokstruct;
    		struct token *tok;
    		tok = &tokstruct;
    		while (__commandline[i] != '\n')
    		{
    			if(__commandline[i] == '\"')
          
    			{
    				i++;
    				if(__commandline[i] == '\"')
    				{
    					tok*[j] = __commandline[i];
    					j++;
    				}
       
    				else if(__commandline[i] == ' ')
    				{
    					i++;
    				}
    			}
    		}

  2. #2
    Dr Dipshi++ mike_g's Avatar
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    If you want to ignore whatever is in quotes, I think something like this should work:
    Code:
    while (__commandline[i] != '\n')
    {
        if(__commandline[i] == '\"')
        {
            do
            {
                i++;
            } while(__commandline[i] != '\"') 
        }
        i++;
    }
    [edit] Actually if a \n char is in the inner loop you will need to break out of both loops as well [/edit]
    Last edited by mike_g; 09-23-2007 at 06:04 PM.

  3. #3
    C++ Witch laserlight's Avatar
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    By the way, why are you using __commandline and __argumentcounter for your variable names instead of just commandline and argumentcounter respectively? I note that according to the standard "all identifiers that begin with an underscore and either an uppercase letter or another underscore are always reserved for any use".
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  4. #4
    and the hat of int overfl Salem's Avatar
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    Look up "finite state machine".
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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