strncmp.c File Reference

#include <string.h>

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Functions
int	strncmp (const char *s1, const char *s2, size_t n)
	Compares at most n characters of two possibly null-terminated arrays. More...

Function Documentation

strncmp()

int strncmp	(	const char *	s1,
		const char *	s2,
		size_t	n
	)

Compares at most n characters of two possibly null-terminated arrays.

Compares at most count characters of two possibly null-terminated arrays. The comparison is done lexicographically.

The behavior is undefined when access occurs past the end of either array s1 or s2. The behavior is undefined when either s1 or s2 is the null pointer.

Parameters

s1	pointers to the null-terminated byte strings to compare
s2	pointers to the null-terminated byte strings to compare
n	maximum number of characters to compare

Returns

Negative value if s1 appears before s2 in lexicographical order. Zero if s1 and s2 compare equal, or if n is zero. Positive value if s1 appears after s2 in lexicographical order.

Definition at line 12 of file strncmp.c.

{
    int r = -1;

    if(s1 == s2)
    {
        // short circuit - same string
        return 0;
    }

    // I don't want to panic with a NULL ptr - we'll fall through and fail
    if(s1 != NULL && s2 != NULL)
    {
        // iterate through strings until they don't match, s1 ends, or n == 0
        for(; n && *s1 == *s2; ++s1, ++s2, n--)
        {
            if(*s1 == 0)
            {
                r = 0;
                break;
            }
        }

        // handle case where we didn't break early - set return code.
        if(n == 0)
        {
            r = 0;
        }
        else if(r != 0)
        {
            r = *s1 - *s2;
        }
    }

    return r;
}

References NULL.

Referenced by strnstr().

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