c语言入门：文件读写操作

本demo 实现了 文件内容解析操作：
如 a 文件中若有 ” 1+2= “
则在b 文件中输出 “1+2=3”；
使用c标准语言实现
以供记录和学习

#include <stdio.h>#include <string.h>#include <stdlib.h>char *getSresult(const char *s,const char *sresult);void move_newline(char *s);int calc(const char *s);int main(){   FILE *p= fopen("/home/renlikang/a.txt","r");   FILE *p1=fopen("/home/renlikang/b.txt","w");   if(p==NULL){       printf("open file failure\n");       return 0;   }   char buf[100]={0};   char sresult[100]={0};   while(!feof(p)){   memset(buf,0,100);   memset(sresult,0,100);   fgets(buf,100,p);   move_newline(buf);   fputs(getSresult(buf,sresult),p1);   }   fclose(p);   fclose(p1);   printf("end\n");   return 0;}char *getSresult(const char *s,const char *sresult){    int result=calc(s);    sprintf(sresult,"%s %d\n",s,result);    printf("%s\n",sresult);    return sresult;}void move_newline(char *s){   int len= strlen(s);   if(s[len-1]=='\n')       s[len-1]=0;}int calc(const char *s){    int len= strlen(s);    int index =0;    char num1[100]={0};    char num2[100]={0};    int int_num1=0;    int int_num2=0;    char opera=0;    while(s[index]){        if(s[index]=='+'||s[index]=='-'||s[index]=='*'||s[index]=='/'){            opera=s[index];            strncpy(num1,s,index);            strncpy(num2,s+index+1,len-index);            int_num1=atoi(num1);            int_num2=atoi(num2);            break;        }        index++;    }   switch(opera){   case '+':       return int_num1+int_num2;   case '-':       return int_num1-int_num2;   case '*':       return int_num1*int_num2;   case '/':       if(int_num2){           return int_num1/int_num2;       }else{           return 0;       }      //扩展运算符；   default:       return 0;   }}