function
<cstring>

strncmp

int strncmp ( const char * str1, const char * str2, size_t num );
Compare characters of two strings
Compares up to num characters of the C string str1 to those of the C string str2.
This function starts comparing the first character of each string. If they are equal to each other, it continues with the following pairs until the characters differ, until a terminating null-character is reached, or until num characters match in both strings, whichever happens first.

Parameters

str1
C string to be compared.
str2
C string to be compared.
num
Maximum number of characters to compare.
size_t is an unsigned integral type.

Return Value

Returns an integral value indicating the relationship between the strings:
return valueindicates
<0the first character that does not match has a lower value in ptr1 than in ptr2
0the contents of both strings are equal
<0the first character that does not match has a grater value in ptr1 than in ptr2

Example

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
/* strncmp example */
#include <stdio.h>
#include <string.h>

int main ()
{
  char str[][5] = { "R2D2" , "C3PO" , "R2A6" };
  int n;
  puts ("Looking for R2 astromech droids...");
  for (n=0 ; n<3 ; n++)
    if (strncmp (str[n],"R2xx",2) == 0)
    {
      printf ("found %s\n",str[n]);
    }
  return 0;
}


Output:

Looking for R2 astromech droids...
found R2D2
found R2A6

See also