串函数

strlen
strcpy
strcmp
strcat
strchr
strstr

int strlen(const char s)
{
int cnt=0;
while(s[cnt]!='\0')cnt++;
return cnt;
}
int strcmp(const char *s1,const char *s2)//0:s1s2; 1:s1>s2; -1:s1<s2;
{
int i=0;
while(s1[i]s2[i]&&s1[i]!='\0')i++;
if(s1[i]==s2[i])return 0;
else if(s1[i]>s2[i])return 1;
else return -1;
}

char *strcpy(char *restrct dst,const char *restrict src)
//把src的字符串拷贝到dst
//restrict表明dst和src不重叠（C99)
//返回dst
{
int i=0;
while(src[i]!='\0')
{
dst[i]=src[i];
}
dst[i]=src[i];//dst[i]='\0';
return dst;
}

char *strchr(const char *s,int c);
char *strrchr(const char *s,int c);
char *strstr(const char *s1,const char *s2);//字符串中寻找字符串
char *strcasestr(const char *s1,const char *s2);//忽略大小写字符串中寻找字符串