从文本内容中提取有效信息

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;      }