NAME¶

strncmp - nonstrings compare

LIBRARY¶

Standard C library (libc, -lc)

SYNOPSIS¶

#include <string.h>  // see memory.h(3head)

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

DESCRIPTION¶

The strncmp() function is similar to strcmp(3), except it compares only the first (at most) n bytes of s1 and s2.

It is equivalent to

memcmp(s1, s2, MIN(MIN(strnlen(s1,n),strnlen(s2,n))+1, n))

RETURN VALUE¶

See memcmp(3).

ATTRIBUTES¶

For an explanation of the terms used in this section, see attributes(7).

STANDARDS¶

C11, POSIX.1-2008.

HISTORY¶

POSIX.1-2001, C89, SVr4, 4.3BSD.

EXAMPLES¶

The program below can be used to demonstrate the operation of strncmp().

$ ./strncmp ABC AB 3;
<strn1> is greater than <strn2> (67)
$ ./strncmp ABC AB 2;
<strn1> and <str2> are equal in the first 2 bytes

// strncmp.c
// Licensed under GNU General Public License v2 or later.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int
main(int argc, char *argv[])
{


    int res;


    if (argc != 4) {


        fprintf(stderr, "Usage: %s <strn1> <strn2> <n>\n", argv[0]);


        exit(EXIT_FAILURE);


    }


    res = strncmp(argv[1], argv[2], atoi(argv[3]));


    if (res == 0) {


        printf("<strn1> and <strn2> are equal");


        printf(" in the first %d bytes\n", atoi(argv[3]));


        printf("\n");


    } else if (res < 0) {


        printf("<strn1> is less than <strn2> (%d)\n", res);


    } else {


        printf("<strn1> is greater than <strn2> (%d)\n", res);


    }


    exit(EXIT_SUCCESS);
}

SEE ALSO¶

memory.h(3head), memcmp(3), strncasecmp(3), wcsncmp(3)