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。