strncmp

 

C

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Strings library

Byte strings

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Null-terminated byte strings

Functions
Character manipulation
isalnum isalpha islower isupper isdigit isxdigit isblank (C99)	iscntrl isgraph isspace isprint ispunct tolower toupper
Conversions to numeric formats
atof atoiatolatoll strtolstrtoll	strtoulstrtoull strtofstrtodstrtold
String manipulation
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strncpy
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String examination
strlen strcmp strncmp strcoll strchr strrchr	strspn strcspn strpbrk strstr strtok
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memchr
memcmp
memset
memcpy
memmove
Miscellaneous
strerror

 

Defined in header <string.h>
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.

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 is less than rhs.

​0​ if lhs is equal to rhs.

Positive value if lhs is greater than rhs.

Example

Run this code

#include <string.h>
#include <stdio.h>
 
int main(void) 
{
    const char* string = "Hello World!";
    const int size = strlen(string);
    //Matches
    int a = strncmp(string, "Hello World!", 5);
    if (a == 0) {
        printf("The 5 first char of each string are matching.\n");
    }
 
    //Greater than
    int b = strncmp(string, "Hello", size);
    if (b >= 1) {
        printf("Left hand side is bigger than right hand side.\n");
    }
 
    //less than
    int c = strncmp(string, "Hello there world!", size);
    if (c <= -1) {
        printf("Left hand side is smaller than right hand side.\n");
    }
}

Output:

The 5 first char of each string are matching.
Left hand side is bigger than right hand side.
Left hand side is smaller than right hand side.

See also

strcmp	compares two strings (function)
memcmp	compares two buffers (function)
strcoll	compares two strings in accordance to the current locale (function)
C++ documentation for strncmp