libc.info: fseek

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`fseek', `fseeko'--set file position

*Synopsis*
     #include <stdio.h>
     int fseek(FILE *FP, long OFFSET, int WHENCE)
     int fseeko(FILE *FP, off_t OFFSET, int WHENCE)
   *Description*
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 `fseek'/`fseeko' to set the position for the file
identified by FP.  The value of OFFSET determines the new position, in
one of three ways selected by the value of WHENCE (defined as macros in
``stdio.h''):
   `SEEK_SET'--OFFSET is the absolute file position (an offset from the
beginning of the file) desired.  OFFSET must be positive.
   `SEEK_CUR'--OFFSET is relative to the current file position.  OFFSET
can meaningfully be either positive or negative.
   `SEEK_END'--OFFSET is relative to the current end of file.  OFFSET
can meaningfully be either positive (to increase the size of the file)
or negative.
   See `ftell'/`ftello' to determine the current file position.
*Returns*
`fseek'/`fseeko' return `0' when successful.  On failure, the result is
`EOF'.  The reason for failure is indicated in `errno': either `ESPIPE'
(the stream identified by FP doesn't support repositioning) or `EINVAL'
(invalid file position).
*Portability*
ANSI C requires `fseek'.
   `fseeko' is defined by the Single Unix specification.
   Supporting OS subroutines required: `close', `fstat', `isatty',
`lseek', `read', `sbrk', `write'.