C Language: strncmp function
(Bounded String Compare)
In the C Programming Language, the strncmp function returns a negative, zero, or positive integer depending on whether the first n characters of the object pointed to by s1 are less than, equal to, or greater than the first n characters of the object pointed to by s2.
The strncmp function will stop comparing if a null character is encountered in either s1 or s2.
Syntax
The syntax for the strncmp function in the C Language is:
int strncmp(const char *s1, const char *s2, size_t n);
Parameters or Arguments
- s1
- An array to compare.
- s2
- An array to compare.
- n
- The number of characters to compare.
Returns
The strncmp function returns an integer. The return values are as follows:
| Return Value | Explanation |
|---|---|
| 0 | s1 and s2 are equal |
| Negative integer | The stopping character in s1 was less than the stopping character in s2 |
| Positive integer | The stopping character in s1 was greater than the stopping character in s2 |
Required Header
In the C Language, the required header for the strncmp function is:
#include <string.h>
Applies To
In the C Language, the strncmp function can be used in the following versions:
- ANSI/ISO 9899-1990
strncmp Example
Let's look at an example to see how you would use the strncmp function in a C program:
/* Example using strncmp by TechOnTheNet.com */
#include <stdio.h>
#include <string.h>
int main(int argc, const char * argv[])
{
/* Create a place to store our results */
int result;
/* Create two arrays to hold our data */
char example1[50];
char example2[50];
/* Copy two strings into our data arrays */
strcpy(example1, "C strncmp at TechOnTheNet.com");
strcpy(example2, "C strncmp is a string function");
/* Compare the two strings provided up to 11 characters */
result = strncmp(example1, example2, 11);
/* If the two strings are the same say so */
if (result == 0) printf("Strings are the same\n");
/* If the first string is less than the second say so
(This is because the 'a' in the word 'at' is less than
the 'i' in the word 'is' */
if (result < 0) printf("Second string is less than the first\n");
return 0;
}
When compiled and run, this application will output:
Second string is less than the first
Similar Functions
Other C functions that are similar to the strncmp function:
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