strstr 的使用和模拟实现
char * strstr ( const char * str1, const char * str2);
Returns a pointer to the first occurrence of str2 in str1, or a null pointer if str2 is not part of str1.
(函数返回字符串str2在字符串str1中第⼀次出现的位置)。
The matching process does not include the terminating null-characters, but it stops there.(字符串的比较匹配不包含 \0 字符,以 \0 作为结束标志)。
/* strstr example */
#include <stdio.h>
#include <string.h>
int main ()
{
char str[] ="This is a simple string";
char * pch;
pch = strstr (str,"simple");
strncpy (pch,"sample",6);
printf("%s\n", str);
return 0;
}
strstr的模拟实现:
char * strstr (const char * str1, const char * str2)
{
char *cp = (char *) str1;
char *s1, *s2;
if ( !*str2 )
return((char *)str1);
while (*cp)
{
s1 = cp;
s2 = (char *) str2;
while ( *s1 && *s2 && !(*s1-*s2) )
s1++, s2++;
if (!*s2)
return(cp);
cp++;
}
return(NULL);
}