C语言文件解析-优快云博客

例如a.txt中有如下内容
$ABC,eqwe,0123,N,we23,E,234
$ABD,fkjd,2454,N,fwer,E,456
$AB,fhew,9478,N,wewf,E,rnju
$ABC,wefn,9834,N,riwqj,E,42
要求：
提取的有效信息为
eqwe,0123,we23
wefn,9834,riwqj
代码实现：
#include<stdio.h>
#include<string.h>
#include<fcntl.h>
#include<unistd.h>
#include<sys/types.h>
int i=0;//存放信息时使用
int main(){
    int fd=open("a.txt",O_RDONLY,0644);
     
    char c;//取出每一个字符
    ssize_t bytes;
    char xinxi[256];//存放提取信息
    if(fd==-1)
    {
        perror("open");
        return -1;
        }
    //不断的读
    while(bytes=(read(fd,&c,sizeof(c)))>0)
    {
        if(c=='$')
            {//文件位置向后移动一位
            read(fd,&c,sizeof(c));
            if(c=='A')
            {
                            read(fd,&c,sizeof(c));
                if(c=='B')
                    {
                                read(fd,&c,sizeof(c));
                        if(c=='C')
                        {
                                    read(fd,&c,sizeof(c));//指针移到逗号前
                                    read(fd,&c,sizeof(c));//
                        if(c!=','){
                            while(c!='N')//提取信息
                            {
                                {xinxi[i]=c;//将有用字符存入数组
                                ++i;
                                            read(fd,&c,sizeof(c));}
 
                            }
                                        read(fd,&c,sizeof(c));//
                            if(c!=',')
                            continue;}
                        }
                        else
                        {
                        while(c!='\n')
                                    read(fd,&c,sizeof(c));
                        continue;//跳出while循环，并开始读取信息
                        }
                    }
            }
            }
    else if(c!='E'&&c!=',')
        {
        xinxi[i]=c;
        ++i;
        }
        else{
            while(c!='\n')
                    read(fd,&c,sizeof(c));
            continue;}
        }//成功读取后的操作
    if(bytes==-1)
    {
        perror("read");
        return -1;
        }
        int m;
        for(m=0;xinxi[m];++m)
            printf("%c",xinxi[m]);
            printf("\n");
     
    return 0;
    }