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[];
    char author[];
    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=;
    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>)
    {
        do{
            printf("please add new book title\n");
            scanf("%s",&bks[i].title);
            printf("please add new book author\n");
            scanf("%s",&bks[i].author);
            printf("please add new book price\n");
            scanf("%d",&bks[i].price);
            i++;
            fwrite(&bks[i],size,,fp);
        }while(i<addList);
    }

}

void read(struct books bks[])
{
    FILE * fp;
    int i=;
    if((fp=fopen(fileName,"r+")) == NULL)
    {
        printf("file open fail");
    }

    rewind(fp);

    while( i<max && fread(&bks[i],size,,fp) == )
    {
        printf("title is %s,author is %s,price is %d\n",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

 #include <string.h>
 #include <stdio.h>
 #include <stdlib.h>

 int main(int argc,char *argv[])
 {
     if(argc<)
     {
         puts("params error");
         exit();
     }

    char *p;
    char c = argv[][];  //传入来的都是字符串，得到需要的字符 ，去掉最后的\0
    int weizhi;

    p = strrchr(argv[],c);//得到字符c在字符串argv[1]中的地址，返回的是字符指针 

    if(p)
      weizhi = p - argv[];  //两个指针相减，得到位置距离
         printf("%d",weizhi);
    else
      puts("not found");   

    return ;
 }

3.字符串查找

 #include <string.h>
 #include <stdio.h>
 #include <stdlib.h>
 #define TRUE   1
 #define FALSE  0
 #define ERROR  0

 int strStart(char *,char *);

 int main(int argc,char *argv[])
 {
      char message[]="hello,welcome to China";
      char find[]="Ch";
      int start = strStart(message,find);
      printf("%d",start);
 }

 int strStart(char * String,char * find)
 {
     int start=-,i=,j=;

     //得到字符串长度
     int StringLen = strlen(String);
     int findLen   = strlen(find);
     //判断是否为空
     if(StringLen<= || findLen<=)
     {
         return FALSE;
     }
     //判断子串的长度是否大于母串的长度
     if(StringLen < findLen)
     {
         return FALSE;
     }
     //开始查找
     for(i=;i<=StringLen;i++)
     {
         if(String[i]==find[j])
         {
             if(start<)
                 start = i;

             j++;
         }else{
             if(j<findLen)
                 start=-;
         }
     }
     return start;
 }