memcmp

Remonter à Mem.h - Index

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.

Remarque :  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++
+	+	+	+