C语言函数strcmp

一些个人的学习笔记而已

STRCMP(3)                                               Linux Programmer's Manual                                              STRCMP(3)

NAME
       strcmp, strncmp - compare two strings

SYNOPSIS
       #include <string.h>

       int strcmp(const char *s1, const char *s2);

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

DESCRIPTION
       The  strcmp() function compares the two strings s1 and s2.  It returns an integer less than, equal to, or greater than zero if s1
       is found, respectively, to be less than, to match, or be greater than s2.

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

RETURN VALUE
       The strcmp() and strncmp() functions return an integer less than, equal to, or greater than zero if s1  (or  the  first  n  bytes
       thereof) is found, respectively, to be less than, to match, or be greater than s2.

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

       ┌────────────────────┬───────────────┬─────────┐
       │Interface           │ Attribute     │ Value   │
       ├────────────────────┼───────────────┼─────────┤
       │strcmp(), strncmp() │ Thread safety │ MT-Safe │
       └────────────────────┴───────────────┴─────────┘
CONFORMING TO
       POSIX.1-2001, POSIX.1-2008, C89, C99, SVr4, 4.3BSD.

SEE ALSO
       bcmp(3), memcmp(3), strcasecmp(3), strcoll(3), string(3), strncasecmp(3), strverscmp(3), wcscmp(3), wcsncmp(3)

COLOPHON
       This  page  is  part  of  release 4.04 of the Linux man-pages project.  A description of the project, information about reporting
       bugs, and the latest version of this page, can be found at http://www.kernel.org/doc/man-pages/.

                                                               2015-08-08                                                      STRCMP(3)

这里说得很明白了

DESCRIPTION
描述
       The  strcmp() function compares the two strings s1 and s2.  It returns an integer less than, equal to, or greater than zero if s1 is found, respectively, to be less than, to match, or be greater than s2.
       strcmp()函数比较两个字符串 s1和s2，最后不管是大于还是小于，都是返回一个整数

       The strncmp() function is similar, except it compares only the first (at most) n bytes of s1 and s2.
       strncmp ( )函数类似,但它只比较了S1和S2的第一个(最多)n个字节。

这个函数，比较两个字符串
设这两个字符串为str1，str2，
若str1==str2，则返回零；（等于）
若str1