如何定位txt中某一行

#include <stdio.h>
#include <string.h>
#define MAXLEN 1000
char ln[MAXLEN];
FILE *f;
int i,z;
int b,n,L;
int main(int argc,char **argv) {
    if (argc<2) {
        printf("Usage:%s fullpathfilename.ext\nget total blank/non-blank/total linenumbers.\n",argv[0]);
        return 1;
    }
    f=fopen(argv[1],"r");
    if (NULL==f) {
        printf("Can not open file [%s]!\n",argv[1]);
        return 2;
    }
    z=0;
    b=0;
    n=0;
    L=0;
    while (1) {
        if (NULL==fgets(ln,MAXLEN,f)) break;
        L=strlen(ln);
        if ('\n'==ln[L-1]) {
            if (0==z) {
                for (i=0;i<L-1;i++) {
                    if (!(' '==ln[i] || '\t'==ln[i])) break;
                }
                if (i<L-1) z=1;//当前行不是空行
            }
            if (0==z) b++; else n++;
            z=0;
        } else {
            if (0==z) {
                for (i=0;i<L;i++) {
                    if (!(' '==ln[i] || '\t'==ln[i])) break;
                }
                if (i<L) z=1;//当前行不是空行
            }
        }
    }
    fclose(f);
    if (L>0 && '\n'!=ln[L-1]) {
        if (0==z) b++; else n++;//最后一行末尾无'\n'也计算
    }
    printf("File:[%s] total blank/non-blank/total linenumbers is %d/%d/%d\n",argv[1],b,n,b+n);
    return 0;
}

------解决方案--------------------
bool file_content(const string& file, string& content)
{
   FILE* fp = fopen( file.c_str(), "rb" );
   if (!fp)  
       return false;

   // Get file length
   fseek(fp, 0, SEEK_END);
   int len = ftell( fp );
   fseek(fp, 0, SEEK_SET);

   content.resize(len);
   fread(&content[0], len, 1, fp);
   fclose(fp);

   return true;
}

void split_lines(const string& s,  vector<string>& lines)
{
   if (s.empty())
       return;

   string line;
   line.reserve(200);

   const char* p = s.c_str();
   for( ; *p; ++p ) {
		line += *p;
       if (*p == '\r') {
			if ( *(p+1) == '\n' ) {
               ++p;
				line += *p;
			}

           lines.push_back(line);
           line = "";
       } else if (*p == '\n') {
           lines.push_back(line);
           line = "";
       }
   }

  if (!line.empty())
      lines.push_back(line);
}

------解决方案--------------------
使用getline读3次即可到达第三行，很方便的。

------解决方案--------------------