strtok & strcpy

This is a discussion on strtok & strcpy within the C Programming forums, part of the General Programming Boards category; I'm using the strtok & strcpy for the program I'm doing. It's sort of a parser of polynomial equations. The ...

  1. #1
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    Question strtok & strcpy

    I'm using the strtok & strcpy for the program I'm doing. It's sort of a parser of polynomial equations. The strtok function works fine. However, when I try to add the strcpy function to save the tokens in arrays, the program compiles but the exe file sort of crashes and closes.

    Here's a sample code of what I'm working on.

    Code:
    #include<stdio.h>
    #include<ctype.h>
    #include<conio.h> 
    #include<string.h>
    #include<stdlib.h>
    #define max 50
    
    main()
    {
         char string[max];
          
         printf("Input string: ");
         scanf("%s", &string);
    
         char tokens[max];
         char *token = NULL;
         int k;
         int i=0;
         token = strtok(string, " ^+-.x");
    
         while(token != '\0')
         {
              printf("%s\n", token);
              strcpy(&tokens[i++], token);        
              token = strtok(NULL, " ^+-.x");
         }
         
         printf("\n\n");
         
         for(k=0; k<=i; k++)
         {
         printf("%s\n", &tokens[k]);
         }
         
         getch();
         return 0;
    }

  2. #2
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    your tokens array should be tokens[STRINGS][MAXLENGTH] ... eg: tokens[10][50] will hold 10 strings each 50 characters long. Also you don't need the & in strcpy... tokens is already a pointer.

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    in the strcpy function, how would the array argument look like?
    Will I change it to something like this? since it's already a 2D array

    strcpy(tokens[i++][k++], token)

  4. #4
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    Quote Originally Posted by firehydrant View Post
    in the strcpy function, how would the array argument look like?
    Will I change it to something like this? since it's already a 2D array

    strcpy(tokens[i++][k++], token)
    No... just use tokens[i++] In the case of strings, the second dimension is not needed. Strings are null terminated so the strcpy() function will discover their length automatically.

    char tokens[max] is a single string... not an array of strings. That's why you need a 2d array.

  5. #5
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    I got it already. Thanks! I didn't change the array argument in the strcpy function. Why did it work? Doesn't the initialization --tokens[STRINGS][MAXLENGTH]-- mean that it's a 2D array?

  6. #6
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    Ok... a single string is an array of characters... eg char x[20]; stores 19 characters.
    If you want an array of multiple strings you are essentially creating an array of arrays of characters. So you need to go the 2d route... eg. char x[10][20]; stores 10 lines of 19 characters.

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