CODEWITHSUNDEEP
cstring
Jacob L.
Jacob L.

Reputation: 11

Strcpy from char* to char[] creating the wrong form

typedef struct Symbol{
    char varName[16];
} Symbol;

...............
Symbol *newSymbol = malloc(sizeof(Symbol));
const char space[2] = " ";


char *String = "Name Test";

//break off the first word from String and put it into name

char *name;
name = strtok(String,space);

//convert the char * to char[16]

char nameArray[16];
strcpy(nameArray,name);

//set newSymbol->varName to the newly created char[16]

newSymbol->varName = nameArray

I have a char * called String. In my actual program, it is read from a file using fgets, I am just calling it "Name Test" for the purposes of this example. I want to take the first word of the string and assign it as the varName in a Symbol. So what should happen is newSymbol->varName is set to "Name". Because strtok returns a char * but I need a char[16] for the struct, I must convert the char * to a char[16].

However, I get this error:

"Error: incompatible types when assigning to type 'char[16]' from type 'char*' 
newSymbol -> varName = nameArray;

So, it seems like strcpy it not actually converting the char * to a char[16]. Even after declaring a char[16] and telling strcpy to put the contents of the char * into it, I still have a char * instead of a char[16]. I need to make it work without changing the struct, so that is not an option here.

How can I convert a char * into a char[16]?

Upvotes: 1

Views: 386

Answers (2)

John Bollinger
John Bollinger

Reputation: 180286

So, it seems like strcpy it not actually converting the char* to a char[16].

No, the problem is that C does not provide for assigning to (whole) arrays. newSymbol->varName is an array of 16 char. You can assign to elements of that array, and you can copy into it with strcpy() or a similar function, but you cannot assign to the whole array.

In your particular code, I'd dispense with variable nameArray, changing this ...

strcpy(nameArray,name);

... to this:

strcpy(newSymbol->varName, name);

(Or perhaps to a similar usage of strncpy(), to protect from overrunning the array bounds.)

Upvotes: 2

R Sahu
R Sahu

Reputation: 206607

You cannot assign the contents of an array using the regular assignment operator in C.

You can use strcpy for strings and memcpy/memset for other data types. (You could use memcpy/memset for strings too but strcpy is simpler)

Instead of

newSymbol -> varName = nameArray;

use

strcpy(newSymbol -> varName, nameArray);

Upvotes: 2

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