C language: detailed explanation of memcmp() usage

1. Introduction to memcmp()

1. Function prototype

int memcmp(const void *str1, const void *str2, size_t n));

2. Parameters

• str1 -Pointer to the memory block.
• str2 -Pointer to the memory block.
• n -the number of bytes to be compared

3. Function

Compare the first n bytes of storage area str1 and storage area str2, mainly for comparing character strings.

4. Header files

#include <string.h>

5. Return value

• From left to right , compare n characters one by one according to the ASCII code value until a different character appears.
• If the return value is <0, it means str1 is less than str2.
• If the return value> 0, it means that str2 is less than str1.
• If the return value = 0, it means that str1 is equal to str2.

Two, memcmp() usage

The memcmp function is mainly used to compare strings.
The specific code is as follows:

#include <stdio.h>
#include <string.h>	

int main(void)
{
    
    
	char *a = "English";
    char *b = "ENGLISH";
    char *c = "english";
    char *d = "English";
    printf("memcmp(a, b):%d\n", memcmp(a, b, 7));//字符串之间的比较 
    printf("memcmp(a, c):%d\n", memcmp(a, c, 7));
    printf("memcmp(a, d):%d\n", memcmp(a, d, 7));
    printf("memcmp(a, \"English\"):%d\n", memcmp(a, "English", 7));
    printf("memcmp(&a[2], \"g\"):%d\n", memcmp(&a[2], "g", 1)); //单个字符的比较 
	return 0;
}

The results are as follows:

memcmp(a, b):1
memcmp(a, c):-1
memcmp(a, d):0
memcmp(a, "English"):0
memcmp(&a[2], "g"):0