Assigning Array to a Struct value in C

Question

For a homework assignment, we are working on CSV parser. I'm trying to get things working, but I've run into an issue. I can't seem to assign a value to "field" value in the struct. In the code they provided they have:

typedef char f_string[MAX_CHARS+1] ;    /* string for each field */

    typedef struct {
        int nfields;                        /* 0 => end of file */
        f_string field[MAX_FIELDS];         /* array of strings for fields */
    } csv_line ;

With the above constants defined at 20 and 15. Looking at what they have, the struct holds and int, and it holds an array that should be populated with the f_string typedef they defined earlier. Alright, cool. I tried to do it this way:

f_string test = "Hello, Bob";
f_string testAgain = "this is dumb, k?";
f_string anArray[MAX_FIELDS] = {*test, *testAgain};

csv_line aLine;
aLine.nfields = 3;
aLine.field = *anArray;

When I make "anArray", if I don't have the dereferences to test and testAgain, I get warnings about making integers to pointers without a cast. So I leave them in. But the line:

aLine.field = *anArray;

Returns the error: "csv.c:87: error: incompatible types in assignment" with or without the pointer there... so I'm not sure how I should be assigning that variable? Help would be appreciated!

Answer 1

You can't assign to an array using =. See this question for a more detailed explanation.

You'll need to copy each string using the strcpy (or the safer strncpy) function:

for (int i = 0; i < aLine.nfields; ++i)
{
  strncpy(aLine.field[i], anArray[i], MAX_CHARS);
}

Also, the test code you provide isn't going to do what you expect.

f_string test = "Hello, Bob";
f_string testAgain = "this is dumb, k?";
f_string anArray[MAX_FIELDS] = {*test, *testAgain};

This will copy the first character of test and testAgain. You need to do something like:

f_string test = "Hello, Bob";
f_string testAgain = "this is dumb, k?";
f_string anArray[MAX_FIELDS];
strcpy(anArray[0], test);
strcpy(anArray[1], testAgain);

Or just:

f_string anArray[MAX_FIELDS] = {"Hello, Bob", "this is dumb, k"};