char *index(const char *s, int c);

#include strings.h

index()用来找出参数s 字符串中第一个出现的参数c地址，然后将该字符出现的地址返回。字符串结束字符(NULL)也视为字符串一部分。

如果找到指定的字符则返回该字符所在地址，否则返回NULL

#include <stdio.h>
#include <strings.h>
int main()
{
    char *s = "abcdef123456abcdef";
    char *p = NULL;
    p = index(s, 'b');
    printf("%s\n", p); 
    return 0;
}

dzlab:~/test/test# ./a.out    
bcdef123456abcdef

char *rindex(const char *s, int c);

rindex()用来找出参数s 字符串中最后一个出现的参数c 地址，然后将该字符出现的地址返回。字符串结束字符(NULL)也视为字符串一部分。

#include <stdio.h>
#include <strings.h>
int main()
{
        char *s = "abcdef123456abcdef";
        char *p = NULL;
        p = rindex(s, 'b');
        printf("%s\n", p);
        return 0;
}

dzlab:~/test/test# ./a.out
bcdef

int bcmp(const void *, const void *, size_t);         /* 用memcmp替代 */
void bcopy(const void *, void *, size_t);             /* 用memcpy, memmove替代 */
void bzero(void *, size_t);                           /* 用memset替代 */
int ffs(int);                                         /* string.h 中有 */
char *index(const char *, int);                       /* 用strchr替代 */
char *rindex(const char *, int);                      /* 用strrchr替代 */
int strcasecmp(const char *, const char *);           /* string.h 中有 */
int strncasecmp(const char *, const char *, size_t);  /* string.h 中有 */

/* We don't need and should not read this file if <string.h> was already
read. The one exception being that if __USE_BSD isn't defined, then
these aren't defined in string.h, so we need to define them here. */