HELP...Use strtok to store strings in global variables...

This is a discussion on HELP...Use strtok to store strings in global variables... within the C Programming forums, part of the General Programming Boards category; Hello, my name is Estella. I have a question about using strtok() to store strings in global variables... because I ...

  1. #1
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    Sep 2004
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    2

    Unhappy HELP...Use strtok to store strings in global variables...

    Hello, my name is Estella. I have a question about using strtok() to store strings in global variables... because I got quite stuck in my functions...

    I declared global variables:
    Code:
    // Global variable
    char *namePtr[100] = {0}; 
    int n;  /*number of components*/
    I wrote a function eat_path to split a string into components:
    e.g. /a/b/c => namePtr[0] = a, namePtr[1] = b, namePtr[2] = c

    In eat_part function:
    Code:
    void eat_path(char *pathname)
    {
    printf("Enter eat_path\n");
    //eat_path() breaks up a pathname into component strings.
    //Example : pathname = /this/is/a/test
    //Then n=4, namePtr[0] ="this", namePtr[1] ="is", namePtr[2] ="a", 
    //namePtr[3] ="test" 
    //The component names will be used to search for a child under its
    parent
    char path[40];
    char delim[] = "/"; /* delimiter is '/' */
    int i = 0, j = 0;
    
    strcpy(path, pathname);
    
    namePtr[j++] = strtok( path, delim );
    
    while(namePtr[j++] = strtok( NULL,delim ));
    
    j--;
    
    n = j;
    
    printf("\nNumber of components: %d\n", n);
    
    for(i = 0; i < n; i++)
    {
    printf("%d %s\n", i, namePtr[i]);
    }
    printf("eat_path ends\n");
    }
    It works fine when I printed the namePtr inside this function, but
    when I print namePtr in another function. it prints out garbage...

    This is another function that calls eat_path:
    Code:
    NODE *namei(char *pathname)
    {
    NODE *ret; 
    int i = 0;
    
    //namei() returns the node pointer of a pathname, or 0;
    //First, call eat_path() to break up pathname into component strings.
    printf("In namei(), pathname = %s\n", pathname);
    eat_path(pathname);
    printf("After eat_path: In namei(), pathname = %s\n", pathname);
    for(int j = 0; j < n; j++)
    printf("%d %s\n", j, namePtr[j]);
    //For each component string, call search_child() to look for the
    child
    //under its parent.
    if (pathname[0] == '/')
    ret = root;
    else
    ret = cwd;
    
    while (ret != 0 && i < n)
    {
    //printf("namePtr[%d] = %s\n", i, namePtr[i]);
    ret = search_child(ret, namePtr[i]);
    i++;
    }
    return ret;
    }
    I checked the content of namePtr right after calling eat_path, so the
    namePtr should contain the same thing when the program is still inside
    eat_path...
    I am so lost... thank you for helping..
    Last edited by Estella; 09-05-2004 at 06:42 PM.

  2. #2
    Code Goddess Prelude's Avatar
    Join Date
    Sep 2001
    Posts
    9,796
    Oh, the joys of global pointers referencing local variables from a different scope than they were declared in. When eat_path returns, path doesn't exist anymore, so your pointers are dangling. You would be better off making a copy of pathname in the calling function and passing that to eat_path rather than making the copy in eat_path.
    My best code is written with the delete key.

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