c语言----程序记录

1.结构体写入文件，读取

#include <stdio.h>
#include <string.h>
#include <stdlib.h> 
#define max 5

struct books{
    char title[20];
    char author[20];
    int price;
};

const char * fileName="books.txt";
int size=sizeof(struct books);

void read(struct books bks[]);
void write(struct books bks[]);
void list(struct books bks[]);
void demo(struct books bks[]);

void main(void)
{
    struct books bks[max];
    
    //write(bks);
    read(bks);

}


void write(struct books bks[])
{
    FILE * fp;
    int i=0;
    int addList;
    if((fp=fopen(fileName,"a+b")) == NULL)
    {
        printf("file open fail"); 
    }
    
    puts("大侠，你想添加几条数据?");
    scanf("%d",&addList);
    
    if(addList>0)
    {
        do{
            printf("please add new book title
");
            scanf("%s",&bks[i].title);
            printf("please add new book author
");
            scanf("%s",&bks[i].author);
            printf("please add new book price
");
            scanf("%d",&bks[i].price);
            i++;
            fwrite(&bks[i],size,1,fp);
        }while(i<addList);
    }
                    
}

void read(struct books bks[])
{
    FILE * fp;
    int i=0;
    if((fp=fopen(fileName,"r+")) == NULL)
    {
        printf("file open fail"); 
    }
    
    rewind(fp);
    
    while( i<max && fread(&bks[i],size,1,fp) == 1)
    {
        printf("title is %s,author is %s,price is %d
",bks[i].title,bks[i].author,bks[i].price);
        i++;
    }
        
}

2. 获取指定字符在字符串的最后的位置

 1 #include <string.h>
 2 #include <stdio.h>
 3 #include <stdlib.h>
 4 
 5 int main(int argc,char *argv[])
 6 {
 7     if(argc<2)
 8     {
 9         puts("params error");
10         exit(1);
11     }
12      
13    char *p;
14    char c = argv[2][0];  //传入来的都是字符串，得到需要的字符 ，去掉最后的 
15    int weizhi;
16    
17    p = strrchr(argv[1],c);//得到字符c在字符串argv[1]中的地址，返回的是字符指针 
18    
19    if(p)
20      weizhi = p - argv[1];  //两个指针相减，得到位置距离 
21         printf("%d",weizhi);
22    else
23      puts("not found");   
24    
25    return 0;
26 }

3.字符串查找

 1 #include <string.h>
 2 #include <stdio.h>
 3 #include <stdlib.h>
 4 #define TRUE   1
 5 #define FALSE  0 
 6 #define ERROR  0
 7 
 8 int strStart(char *,char *);
 9 
10 int main(int argc,char *argv[])
11 {
12      char message[]="hello,welcome to China"; 
13      char find[]="Ch";
14      int start = strStart(message,find);
15      printf("%d",start);
16 }
17 
18 int strStart(char * String,char * find)
19 {
20     int start=-1,i=0,j=0;
21     
22     //得到字符串长度 
23     int StringLen = strlen(String);
24     int findLen   = strlen(find);
25     //判断是否为空
26     if(StringLen<=0 || findLen<=0)
27     {
28         return FALSE;
29     }
30     //判断子串的长度是否大于母串的长度
31     if(StringLen < findLen)
32     {
33         return FALSE;
34     } 
35     //开始查找 
36     for(i=0;i<=StringLen;i++)
37     {
38         if(String[i]==find[j])
39         {
40             if(start<0)
41                 start = i;
42             
43             j++;    
44         }else{
45             if(j<findLen)
46                 start=-1;
47         }
48     }
49     return start;
50 }