C strncmp

int strncmp(const char *string1, const char *string2, size_t count);

與strcmp類似，只是多了限定比較長度。(strcmp 參考)

功能：比較兩個字串

回傳：1,0,-1(據自己實驗下來，會依據第一個發現不同的字元進行比大小，並回傳結果)

回傳代表意思

-1: string1 < string2

0: string1 = string2

1: string1 > string2

注意：一定要確保字串中有空字元”\0”

程式碼(指定長度內有不同)

此處指定比較長度為7

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

int main(void)
{
  int result = 0;
  result = strncmp(string1,string2,7);
  printf("string1 compare with string2.Result:%d\n\n",result);

  result = strncmp(string2,string1,7);
  printf("string2 compare with string1.Result:%d\n\n",result);

  result = strncmp(string1,string1,7);
  printf("string1 compare with string1.Result:%d\n\n",result);
  return 0;
}

執行結果

程式碼(指定長度內無不同)

此處指定比較長度為4

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

char string1[] = "string1";
char string2[] = "string2";

int main(void)
{
  int result = 0;
  result = strncmp(string1,string2,4);
  printf("string1 compare with string2.Result:%d\n\n",result);

  result = strncmp(string2,string1,4);
  printf("string2 compare with string1.Result:%d\n\n",result);

  result = strncmp(string1,string1,4);
  printf("string1 compare with string1.Result:%d\n\n",result);
  return 0;
}

執行結果

參考資料

https://zh.m.wikipedia.org/zh-tw/String.h#%E5%87%BD%E6%95%B0

https://www.ibm.com/docs/en/i/7.4?topic=functions-strncmp-compare-strings#strncmp