错误无效的操作数到C中的二进制表达式

Question

I am trying to move one position back in the stdin.Using this code:

fpos_t fPos;
fgetpos(stdin,&fPos);
fPos -= 1;
fsetpos(stdin,&fPos);

But I get this error:

 invalid operands to binary expression ('fpos_t'(aka '_G_fpos_t') and 'int')

But my question is why I get it? Then how can I set the fPos to one position behind?

Thanks.

Answer 1

fpos_t is a structure, not an int, and it's only meant to be used in fgetpos and fsetpos calls - you're not supposed to manipulate it directly

Use fseek() with SEEK_CUR argument to manipulate the current stream position