# std::strncmp

From cppreference.com
< cpp‎ | string‎ | byte

Defined in header `<cstring>` |  |
int strncmp( const char* lhs, const char* rhs, size_t count ); |  |

Compares at most `count` characters of two null-terminated byte strings. The comparison is done lexicographically.

The sign of the result is the sign of the difference between the values of the first pair of characters (both interpreted as unsigned char) that differ in the strings being compared.

The behavior is undefined if `lhs` or `rhs` are not pointers to null-terminated strings.

Characters following the null character are not compared.

### Parameters

lhs, rhs | - | pointers to the null-terminated byte strings to compare
count | - | maximum number of characters to compare

### Return value

Negative value if `lhs` appears before `rhs` in lexicographical order.

Zero if `lhs` and `rhs` compare equal.

Positive value if `lhs` appears after `rhs` in lexicographical order.

### Example

Run this code

    #include <cstring>
    #include <iostream>

    void demo(const char* lhs, const char* rhs, int sz)
    {
        int rc = std::strncmp(lhs, rhs, sz);
        if(rc == 0)
            std::cout << "First " << sz << " chars of ["
                      << lhs << "] equal [" << rhs << "]\n";
        else if(rc < 0)
            std::cout << "First " << sz << " chars of ["
                      << lhs << "] precede [" << rhs << "]\n";
        else if(rc > 0)
            std::cout << "First " << sz << " chars of ["
                      << lhs << "] follow [" << rhs << "]\n";
    }
    int main()
    {
        demo("Hello, world!", "Hello, everybody!", 13);
        demo("Hello, everybody!", "Hello, world!", 13);
        demo("Hello, everybody!", "Hello, world!", 7);
        demo("Hello, everybody!" + 12, "Hello, somebody!" + 11, 5);
    }

Output:

    First 13 chars of [Hello, world!] follow [Hello, everybody!]
    First 13 chars of [Hello, everybody!] precede [Hello, world!]
    First 7 chars of [Hello, everybody!] equal [Hello, world!]
    First 5 chars of [body!] equal [body!]

### See also

strcmp | compares two strings (function)
wcsncmp | compares a certain amount of characters from two wide strings (function)
memcmp | compares two buffers (function)
strcoll | compares two strings in accordance to the current locale (function)
C documentation for strncmp

Retrieved from "http://en.cppreference.com/mwiki/index.php?title=cpp/string/byte/strncmp&oldid=88191"