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FSEEK(3)              DragonFly 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 offset, int whence);

     long
     ftell(FILE *stream);

     void
     rewind(FILE *stream);

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

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

     #include <sys/types.h>

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

     off_t
     ftello(FILE *stream);


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)
     and ungetwc(3) functions on the same stream.

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

     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)).

     Since rewind() does not return a value, an application wishing to detect
     errors should clear errno, then call rewind(), and if errno is non-zero,
     assume an error has occurred.

     The fseeko() function is identical to fseek(), except it takes an off_t
     argument instead of a long.  Likewise, the ftello() function is identical
     to ftell(), except it returns an off_t.

     The fgetpos() and fsetpos() functions are alternate interfaces for
     retrieving and setting the current position in the file, similar to
     ftell() and fseek(), except that the current position is stored in an
     opaque object of type fpos_t pointed to by pos.  These functions provide
     a portable way to seek to offsets larger than those that can be repre-
     sented by a long int.  They may also store additional state information
     in the fpos_t object to facilitate seeking within files containing multi-
     byte characters with state-dependent encodings.  Although fpos_t has tra-
     ditionally been an integral type, applications cannot assume that it is;
     in particular, they must not perform arithmetic on objects of this type.

     If the stream is a wide character stream (see fwide(3)), the position
     specified by the combination of offset and whence must contain the first
     byte of a multibyte sequence.


RETURN VALUES

     The rewind() function returns no value.

     The fgetpos(), fseek(), fseeko(), and fsetpos() functions return the
     value 0 if successful; otherwise the value -1 is returned and the global
     variable errno is set to indicate the error.

     Upon successful completion, ftell() and ftello() return the current off-
     set.  Otherwise, -1 is returned and the global variable errno is set to
     indicate the error.


ERRORS

     [EBADF]            The stream argument is not a seekable stream.

     [EINVAL]           The whence argument is invalid or the resulting file-
                        position indicator would be set to a negative value.

     [EOVERFLOW]        The resulting file offset would be a value which can-
                        not be represented correctly in an object of type
                        off_t for fseeko() and ftello() or long for fseek()
                        and ftell().

     [ESPIPE]           The file descriptor underlying stream is associated
                        with a pipe or FIFO or file-position indicator value
                        is unspecified (see ungetc(3)).

     The functions 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), fwide(3), ungetc(3), ungetwc(3)


STANDARDS

     The fgetpos(), fsetpos(), fseek(), ftell(), and rewind() functions con-
     form to ISO/IEC 9899:1990 (``ISO C90'').

     The fseeko() and ftello() functions conform to IEEE Std 1003.1-2001
     (``POSIX.1'').

DragonFly 3.5                   March 19, 2004                   DragonFly 3.5

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