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FSEEK(3)                 BSD 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
     fgetpos(FILE *restrict stream, fpos_t *restrict pos);

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

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

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

     long
     ftell(FILE *stream);

     off_t
     ftello(FILE *stream);

     void
     rewind(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() func-tion function
     tion 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 indicator 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 off-sets offsets
     sets larger than those that can be represented by a long int.  They may also store additional state
     information in the fpos_t object to facilitate seeking within files containing multibyte characters
     with state-dependent encodings.  Although fpos_t has traditionally 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 offset.  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 cannot 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 fileposition
                        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).

LEGACY SYNOPSIS
     #include <stdio.h>
     #include <sys/types.h>

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

     The include file <sys/types.h> supplies the definition for off_t.

SEE ALSO
     lseek(2), clearerr(3), fwide(3), ungetc(3), ungetwc(3), compat(5)

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

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

BSD                             March 19, 2004                             BSD

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