C：遍历一串字符串

Question

I'm currently learning C and am struggling with how to iterate through an array of strings.
Let's just say I define an array, like so:

char* argv_custom[] = {"--debug", "--verbose", "--test", "--ultimate"};

Now, how would I go about determining the number of strings within argv_custom? (eg argc_custom)
Am I going the right way about this in the first place? Also, is it possible to do something like:

Pseudocode

if ('--debug' in argv_custom) { // do stuff }

Answer 1

Now, how would I go about determining the number of strings within argv_custom?

The canonical way :

int argc_custom = sizeof(argv_custom) / sizeof(argv_custom[0]);

Note: This only works on the array itself, as soon as you have a pointer (such as if you pass argv_custom to a function), it no longer works:

char **p = argv_custom;
int argc_custom = sizeof(p) / sizeof(p[0]);  // No me gusta

---

is it possible to do something like: ...

There's no shortcut. You would have to iterate over each string, and do strcmp . Of course, you could (and probably should) wrap this behaviour into a function.

Answer 2

you can do sizeof(argv_custom)/sizeof(argv_custom[0]) . This calculates the total length of the array divided by the size of every single element.

Answer 3

I've had this question quite a few times and from what I've found my favorite solution is to just iterate through the pointer until null . sizeof stops working as soon as you start using functions and passing the arrays around.

Here's a paradigm I've used time and time again in my assignments and it's been really helpful. The exact same thing can be used for getting the length of a cstring or iterating through its characters.

char* argv_custom[] = {"--debug", "--verbose", "--test", "--ultimate"};
char **temp = argv_custom;
int size = 0;
while (*temp) {
    ++size;
    ++temp;
}

This is not preferred over using sizeof , however it's an alternative when you want to loop through it.