C语言提取字符串

 1 #include<stdio.h>
 2 #include<string.h>
 3 
 4 int myatoi(char str[])
 5 {
 6     int len=strlen(str);
 7     char *p=str+len-1;
 8     int sum=0,i=0,num;
 9     while(p>=str)
10     {
11         num=*p-48;
12         for(int j=0;j<i;j++)
13         {
14             num*=10;
15         }
16         i++;
17         sum+=num;
18         p--;
19     }
20     return sum;
21 }
22 
23 int getUserId(char *p,int *n)
24 {
25     char *q=strstr(p,"UserId=");
26     if(q==NULL)
27         return 0;
28     q+=7;
29     char str[20];
30     int i=0;
31     while(*q>=‘0‘ && *q<=‘9‘)
32     {
33         str[i]=*q;
34         i++;
35         q++;
36     }
37     str[i]=‘\0‘;
38     *n=myatoi(str);
39     return 1;
40 }
41 int main()
42 {
43     char str[]="https://www.cnblogs.com/ysjd UserId=123456 passwd=513920";
44     int n;
45     int ret=getUserId(str,&n);
46     if(ret==0)
47     {
48         printf("not found\n");
49     }
50     else
51     {
52         printf("UserId=%d\n",n);
53     }
54 }