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`fsetpos'--restore position of a stream or file

     #include <stdio.h>
     int fsetpos(FILE *FP, const fpos_t *POS);
Objects of type `FILE' can have a "position" that records how much of
the file your program has already read.  Many of the `stdio' functions
depend on this position, and many change it as a side effect.
   You can use `fsetpos' to return the file identified by FP to a
previous position `*POS' (after first recording it with `fgetpos').
   See `fseek' for a similar facility.
`fgetpos' returns `0' when successful.  If `fgetpos' fails, the result
is `1'.  The reason for failure is indicated in `errno': either
`ESPIPE' (the stream identified by FP doesn't support repositioning) or
`EINVAL' (invalid file position).
ANSI C requires `fsetpos', but does not specify the nature of `*POS'
beyond identifying it as written by `fgetpos'.
   Supporting OS subroutines required: `close', `fstat', `isatty',
`lseek', `read', `sbrk', `write'.