.. _fseek:

Setting the file position indicator
===================================

As calls are made to read or write to a file, file position
indicator is moved. These functions can be used to explicitly set
the file position indicator (fpi):

    ``rewind(FILE *fp)``

        - Set the fpi to beginning of file.

    ``fseek( FILE *fp, long offset, int place )``

        - Move to offset bytes from place. place must be one of SEEK_SET,
          SEEK_CUR, SEEK_END which is for beginning, current, or end of the
          file.

    ``long ftell(FILE *fp)``

        - Returns the current file position relative to the beginning of the
          file.

    ``fgetpos(FILE *fp, fpos_t *pos)``

        - Like `ftell()` except position is stored in a data structure.

    ``fsetpos(FILE *fp, fpos_t *pos)``

        - Like `fseek()` except position is passed to the function in a data
          structure.


Here are two ways to do a bookmark.

::

    FILE *fp;
    long marker;
    fpos_t altmarker;
    
    ...
    marker = ftell(fp);             /* set the bookmark */
    ...
    fseek( fp, marker, SEEK_SET );  /* move to bookmark */
    
    fgetpos( fp, &altmarker );      /* set the bookmark */
    ...                                                    
    fsetpos( fp, &altmarker );      /* move to bookmark */