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cstringfunction
Zen Cicevic
Zen Cicevic

Reputation: 321

Passing string to a function in C - with or without pointers?

When I'm passing a string to the function sometimes I use

char *functionname(char *name[256])

and sometimes I use it without pointers (for example:

char functionname(char name[256])

My question is,when do I need to use pointers ? Often I write programs without pointers and it works,but sometimes it doesn't.

Upvotes: 30

Views: 193811

Answers (3)

Adam Zalcman
Adam Zalcman

Reputation: 27233

The accepted convention of passing C-strings to functions is to use a pointer:

void function(char* name)

When the function modifies the string you should also pass in the length:

void function(char* name, size_t name_length)

Your first example:

char *functionname(char *name[256])

passes an array of pointers to strings which is not what you need at all.

Your second example:

char functionname(char name[256])

passes an array of chars. The size of the array here doesn't matter and the parameter will decay to a pointer anyway, so this is equivalent to:

char functionname(char *name)

See also this question for more details on array arguments in C.

Upvotes: 60

Nicola Musatti
Nicola Musatti

Reputation: 18218

Assuming that you meant to write

char *functionname(char *string[256])

Here you are declaring a function that takes an array of 256 pointers to char as argument and returns a pointer to char. Here, on the other hand,

char functionname(char string[256])

You are declaring a function that takes an array of 256 chars as argument and returns a char.

In other words the first function takes an array of strings and returns a string, while the second takes a string and returns a character.

Upvotes: 3

Anickyan
Anickyan

Reputation: 414

An array is a pointer. It points to the start of a sequence of "objects".

If we do this: ìnt arr[10];, then arr is a pointer to a memory location, from which ten integers follow. They are uninitialised, but the memory is allocated. It is exactly the same as doing int *arr = new int[10];.

Upvotes: 0

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