strncmp Function

Compare two strings, up to a specified number of characters.

Include

<string.h>

Prototype

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

Arguments

s1

first string

s2

second string

n

number of characters to compare

Return Value

Returns a positive number if s1 is greater than s2, zero if s1 is equal to s2 or a negative number if s1 is less than s2.

Remarks

strncmp returns a value based on the first character that differs between s1 and s2. Characters that follow a null character are not compared.

Example

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

int main(void)
{
  char buf1[50] = "Where is the time?";
  char buf2[50] = "Where did they go?";
  char buf3[50] = "Why?";
  int res;

  printf("buf1 : %s\n", buf1);
  printf("buf2 : %s\n", buf2);
  printf("buf3 : %s\n\n", buf3);

  res = strncmp(buf1, buf2, 6);
  if (res < 0)
    printf("buf1 comes before buf2\n");
  else if (res == 0)
    printf("6 characters of buf1 and buf2 "
           "are equal\n");
  else
   printf("buf2 comes before buf1\n");
  printf("\n");

  res = strncmp(buf1, buf2, 20);
  if (res < 0)
    printf("buf1 comes before buf2\n");
  else if (res == 0)
    printf("20 characters of buf1 and buf2 "
           "are equal\n");
  else
    printf("buf2 comes before buf1\n");
  printf("\n");

  res = strncmp(buf1, buf3, 20);
  if (res < 0)
    printf("buf1 comes before buf3\n");
  else if (res == 0)
    printf("20 characters of buf1 and buf3 "
           "are equal\n");
else
    printf("buf3 comes before buf1\n");
}

Example Output

buf1 : Where is the time?
buf2 : Where did they go?
buf3 : Why?

6 characters of buf1 and buf2 are equal

buf2 comes before buf1

buf1 comes before buf3