My result is 1 but the length of string i entered is longer

Question

#include <stdio.h>
int length(char *point)
{
    int n=0;


    if (*point!='\0')
    {
        point++;
        n++;
    }
    return n;

}
void main()
{

    int m;
    char *point;
    char chars[80];
    printf ("please enter a chars\n");
    gets(chars);
    point=chars;
    m=length(chars);

    printf("The length of the chars is %d.\n",m);

}

I want to ask why the "n" can't be added? I think the problem is about the use of point,but i can't find it. Thanks.

and if you use built-in function `strlen` instead of custom one `length`? — unalignedmemoryaccess, Jun 09 '17 at 11:16
@Badda `int main()` is a MUST (_almost_), while `return 0;` is entirely optional. :) — Sourav Ghosh, Jun 09 '17 at 11:20
Plus never use `gets` as it has been deprecated and it is dangerous. https://stackoverflow.com/questions/1694036/why-is-the-gets-function-so-dangerous-that-it-should-not-be-used — Davide Spataro, Jun 09 '17 at 11:24

Badda · Answer 1 · 2017-06-09T14:27:34.597

6

size_t length(const char *point)
{
    size_t n = 0;       
    while (*point != '\0') // Need to loop to iterate through point
    {
        point++;
        n++;
    }
    return n;
}

I would use it in the main like that :

int main(void)
{
    char chars[80];
    printf ("Please enter a chars\n");

    scanf("%79s", chars); 
    // The 79 is there to limit the input to the size you allocated in chars[80]
    // Thus avoiding buffer overflow

    size_t m = length(chars);
    printf("The length of the chars is %zu.\n",m);
    return 0;
}

You forget to iterate through the string. You incremented the pointer but that's all. Also, I recommend using strlen() which does exactly what you intend to do.

Using strlen():

int main(void)
{
    char chars[80];
    printf ("Please enter a chars\n");
    scanf("%79s", chars);
    size_t m = strlen(chars);
    printf("The length of the chars is %zu.\n", m);
    return 0;
}

edited Jun 09 '17 at 14:27

answered Jun 09 '17 at 11:18

Badda

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Also I would use `size_t length(const char* point)` over `size_t length(char* point)` for const correctness, since you're not changing the characters. – Andre Kampling Jun 09 '17 at 11:21
@AndreKampling You are correct. I just have a little doubt, isn't it `char const* point` to make a const string ? – Badda Jun 09 '17 at 11:23
1

Pointer to const char: `const char* point` == `char const* point`. The only diffrence is: `char* const point` where the pointer is constant to a non const char. – Andre Kampling Jun 09 '17 at 11:25
@tilz0R: No it isn't he changed `if` with `while`. – Andre Kampling Jun 09 '17 at 11:27
@AndreKampling right now there is an `if` in the question. Could not spot any `while`. – Jabberwocky Jun 09 '17 at 11:29
@MichaelWalz: Question: `if (*point!='\0')` != This answer: `while (*point != '\0')`. Am I blind? – Andre Kampling Jun 09 '17 at 11:30
@AndreKampling sorry I misunderstood your comment, forget it. – Jabberwocky Jun 09 '17 at 11:32
2

`scanf("%s", &chars);` → `scanf("%79s", chars);`. `%s` expects a `char*`, not a `char (*)[80]` – Spikatrix Jun 09 '17 at 11:40
@CoolGuy Ok for the `&`. So `"%79s"` limits the string to 79 char ? I didn't know that – Badda Jun 09 '17 at 11:44
2

Yes. Its the length specifier and tells `scanf` to read at most 79 (in this case) characters (+1 for the NUL-terminator `\0`), thus preventing buffer overflows – Spikatrix Jun 09 '17 at 11:46
I used while instead of if and it worked .Thanks for all of your answers. – shiro Jun 09 '17 at 12:14
@chux Thanks. Accordingly to that meta post, I thought pasting it as a comment on the post would be the best. – Badda Jun 09 '17 at 14:33
Maybe after a fews days. IAC, you are on way up - patience. – chux - Reinstate Monica Jun 09 '17 at 14:35

score 0 · Answer 2 · answered Jun 09 '17 at 11:59

0

You don't have a loop inside your function length(). The if is only evaluated once.

Add (or replace the if with) a loop statement

/* loop */ {
    if (*point!='\0') { /* ... */ }
}

answered Jun 09 '17 at 11:59

pmg

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My result is 1 but the length of string i entered is longer

2 Answers2