strchr实现

char* strchr(char*s,charc)

{

while(*s!='\0'&&*s!=c)

{

++s;

}

return*s==c?s:NULL;

}









// strchr.c查找字符串s中首次出现字符c的位置

#include<stdio.h>

#include<string.h>



char* my_strchr(const char *s1, const char *s2)

{

    const char *p = s1;

    const size_t len = strlen (s2);

    for(;(p = strchr (p, *s2))!=0;p++)

    {

        if(strncmp(p,s2,len)==0)

        return(char*)p;

    }

    return(0);

}



int main(void)

{

/*

    char string[17];

    char *ptr, c = 'a';

    strcpy(string, "This is a string");

    ptr = strchr(string, c);

    //ptr = my_strchr(string, c);

    if (ptr)

    {

        *ptr='\0';

        printf("%s\n", string);

        //printf("The character %c is at position: %d,ptr=%s,string=%s\n", c, ptr-string,ptr,string);

    }

    else

        printf("The character was not found\n");

    return 0; 

*/

/*

char *ifName="atm/(0_0_32)",   *pStart,      *pEnd,     p[16];

pStart=strchr(ifName,'(');

pEnd=strchr(ifName,')');

p[0]='\0';

strncat(p,pStart+1,pEnd-pStart-1);

printf("%s,pStart=%d,pEnd=%d\n",p,pStart,pEnd);

*/



/*

   char wanL2PvcName[32];

   char *pStart,*pEnd,*pvcname='\0';

   strncpy(wanL2PvcName, "atm0/(0_0_45)", sizeof(wanL2PvcName)-1);

   if ((pStart = strchr(wanL2PvcName, '(')) && (pEnd = strchr(wanL2PvcName, ')')))

   {

      //now wanL2PvcName is "0_0_32", "0_0_45" etc. 

      wanL2PvcName[0]='\0';

      strncat(wanL2PvcName,pStart+1,pEnd-pStart-1);

      printf("wanL2PvcName=%s\n",wanL2PvcName);

   }

*/



        char *name="ipoe_0_0_32",*pvcname;

        if (name != NULL)

        {

            *name = '\0';

        }

            if(pvcname = strchr(name,'_'))

            {

                if(strcmp(pvcname+1,"0_0_32") == 0)

                    printf("pvcname+1=%s\n\n",pvcname+1);

            }



}

//函数strstr()，可以用于在一个较长的字符串中查找匹配的字符串或字符。

//string strstr(string str,string needle)

//如果找到了needle的准确位置，将从needle的前面返回一个字符串。否则返回false。如果不止一个needle，返回的字符串从出现的第一个needle开始。

//strchr和strstr()类似。

//stristr()不区分大小写,strchr区分大小写

//strrchr()是从最后出现needle的位置开始返回string值。