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FSEEK(3)                   Library Functions Manual                   FSEEK(3)

NAME
     fgetpos, fseek, fseeko, fsetpos, ftell, ftello, rewind - reposition a
     stream

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <stdio.h>

     int
     fseek(FILE *stream, long int offset, int whence);

     int
     fseeko(FILE *stream, off_t offset, int whence);

     long int
     ftell(FILE *stream);

     off_t
     ftello(FILE *stream);

     void
     rewind(FILE *stream);

     int
     fgetpos(FILE * restrict stream, fpos_t * restrict pos);

     int
     fsetpos(FILE * restrict stream, const fpos_t * restrict pos);

DESCRIPTION
     The fseek() function sets the file position indicator for the stream
     pointed to by stream.  The new position, measured in bytes, is obtained
     by adding offset bytes to the position specified by whence.  If whence is
     set to SEEK_SET, SEEK_CUR, or SEEK_END, the offset is relative to the
     start of the file, the current position indicator, or end-of-file,
     respectively.  A successful call to the fseek() function clears the end-
     of-file indicator for the stream and undoes any effects of the ungetc(3)
     function on the same stream.

     The fseeko() function is identical to the fseek() function except that
     the offset argument is of type off_t.

     The ftell() function obtains the current value of the file position
     indicator for the stream pointed to by stream.

     The ftello() function is identical to the ftell() function except that
     the return value is of type off_t.

     The rewind() function sets the file position indicator for the stream
     pointed to by stream to the beginning of the file.  It is equivalent to:

           (void)fseek(stream, 0L, SEEK_SET)

     except that the error indicator for the stream is also cleared (see
     clearerr(3)).

     In this implementations, "fpos_t" is a complex object that represents
     both the position and the parse state of the stream, making these
     routines the only way to portably reposition a text stream.  The pos
     argument of fsetpos() must always be initialized by a call to fgetpos().

RETURN VALUES
     The rewind() function returns no value.

     Upon successful completion, fgetpos(), fseek(), fseeko(), and fsetpos()
     return 0, whereas the functions ftell() and ftello() return the current
     offset.  On failure, fseek(), fseeko(), ftell(), and ftello() return -1,
     while fgetpos() and fsetpos() return a nonzero value.

     On error all functions set the global variable errno to indicate the
     error.  Since the rewind() function does not return an error code,
     applications need to clear errno before calling it in order to detect
     errors.

ERRORS
     [EBADF]            The stream specified is not a seekable stream.

     [EINVAL]           The whence argument to fseek() was not SEEK_SET,
                        SEEK_END, or SEEK_CUR.

     [EOVERFLOW]        For ftell(), the current file offset cannot be
                        represented correctly in an object of type long.

     The function fgetpos(), fseek(), fseeko(), fsetpos(), ftell(), ftello(),
     and rewind() may also fail and set errno for any of the errors specified
     for the routines fflush(3), fstat(2), lseek(2), and malloc(3).

SEE ALSO
     lseek(2), clearerr(3), ungetc(3)

STANDARDS
     The fgetpos(), fsetpos(), fseek(), ftell(), and rewind() functions
     conform to ANSI X3.159-1989 ("ANSI C89").  The fseeko() and ftello()
     functions conform to X/Open System Interfaces and Headers Issue 5
     ("XSH5").

BUGS
     The fgetpos() and fsetpos() functions don't store/set shift states of the
     stream in this implementation.

NetBSD 10.99                  September 11, 2021                  NetBSD 10.99