C语言 strncmp()函数

在上一个教程中，我们讨论了strcmp()函数，它用于比较两个字符串。在本指南中，我们将讨论 strncmp()函数，它与strcmp()相同，但strncmp()比较仅限于函数调用期间指定的字符数。例如，strncmp(str1, str2, 4)仅比较字符串str1和str2的前四个字符。

C strncmp()函数声明

int strncmp(const char *str1, const char *str2, size_t n)

str1 – 第一个字符串

str2 – 第二个字符串

n – 需要比较的字符数。

strncmp()的返回值

此函数仅比较字符串的前n个（指定数量）字符，并根据比较返回以下值。

例 1：C 中的strncmp()函数

#include <stdio.h>#include <string.h>int main () {   char str1[20];   char str2[20];   int result;   //Assigning the value to the string str1   strcpy(str1, "hello");   //Assigning the value to the string str2   strcpy(str2, "helLO WORLD");   //This will compare the first 3 characters   result = strncmp(str1, str2, 3);   if(result > 0) {      printf("ASCII value of first unmatched character of str1 is greater than str2");   } else if(result < 0) {      printf("ASCII value of first unmatched character of str1 is less than str2");   } else {      printf("Both the strings str1 and str2 are equal");   }   return 0;}

输出：

Both the strings str1 and str2 are equal

strncmp()函数的示例 2

让我们稍微改变上面的例子。这里我们比较字符串的前四个字符。

#include <stdio.h>#include <string.h>int main () {   char str1[20];   char str2[20];   int result;   strcpy(str1, "hello");   strcpy(str2, "helLO WORLD");   //This will compare the first 4 characters   result = strncmp(str1, str2, 4);   if(result > 0) {      printf("ASCII value of first unmatched character of str1 is greater than str2");   } else if(result < 0) {      printf("ASCII value of first unmatched character of str1 is less than str2");   } else {      printf("Both the strings str1 and str2 are equal");   }   return 0;}

输出：

ASCII value of first unmatched character of str1 is greater than str2