memcmp

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Header File

mem.h, string.h

Category

Memory and String Manipulation Routines, Inline Routines

Prototype

int memcmp(const void *s1, const void *s2, size_t n);

Description

Compares two blocks for a length of exactly n bytes.

memcmp is available on UNIX System V systems.

memcmp compares the first n bytes of the blocks s1 and s2 as unsigned chars.

Return Value

Because it compares bytes as unsigned chars, memcmp returns a value that is

• < 0 if s1 is less than s2
• = 0 if s1 is the same as s2
• > 0 if s1 is greater than s2

For example,

memcmp("\xFF", "\x7F", 1)

returns a value greater than 0.

Note: If you are using the intrinsic version of these functions, the case of n = 0 will return NULL.

Example

#include <stdio.h>
#include <string.h>
int main(void)
{
   char *buf1 = "aaa";
   char *buf2 = "bbb";
   char *buf3 = "ccc";
   int stat;
   stat = memcmp(buf2, buf1, strlen(buf2));
   if (stat > 0)
      printf("buffer 2 is greater than buffer 1\n");
   else
      printf("buffer 2 is less than buffer 1\n");
   stat = memcmp(buf2, buf3, strlen(buf2));
   if (stat > 0)
      printf("buffer 2 is greater than buffer 3\n");
   else
      printf("buffer 2 is less than buffer 3\n");
   return 0;
}

Portability

POSIX	Win32	ANSI C	ANSI C++
+	+	+	+