Find length of array of strings in C

Question

I have a dynamic array of c-strings

char **my_strings = (char**)malloc(50 * sizeof(char*));

and I want to find it's actual length (how many strings it actually contains). How can I do this?

Read How to Ask and fdollow the advice. Provide a minimal reproducible example. — too honest for this site
– too honest for this site, Commented Mar 21, 2017 at 20:24
You don't have an array of c-strings. You have a pointer to pointers of char. While similar, not the entirely same thing. — Bauss
– Bauss, Commented Mar 21, 2017 at 20:25
@StoryTeller I tried to do this, but it doesn't work : while (!strings[count] == NULL) count++; — Kiramm
– Kiramm, Commented Mar 21, 2017 at 20:25
@StoryTeller Oh yes. C has something for every coding style in its long history. argv[argc] is NULL C11 §5.1.2.2.1 2, C also set the last element to NULL. Is that redundant? Did I ask that before? Courtesy of department of redundancy department ;-) ;-) — chux
– chux, Commented Mar 21, 2017 at 21:05

Bathsheba · Accepted Answer · 2017-03-21 20:32:48Z

3

You can't tell: it's your job to keep track of the size, or to use a magic value (NULL, say) to mark the final element.

Note that the c runtime probably keeps track of the amount of memory allocated, but this is not exposed to you in any portable way.

answered Mar 21, 2017 at 20:32

Bathsheba

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Comments

Marcus · Accepted Answer · 2017-03-21 20:27:12Z

2

Make the array be terminated with a NULL pointer, then just do:

size_t count = 0;
while (my_strings[count] != NULL) {
    ++count;
}

answered Mar 21, 2017 at 20:27

Marcus

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pmg · Accepted Answer · 2017-03-21 20:43:05Z

0

A char * is not a "string": it is a pointer. Strings are arrays where one of its elements is '\0'.

Pointers and arrays are different!

Check section 6 of the c-faq.

answered Mar 21, 2017 at 20:43

pmg

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