--- /dev/null
+.\" Copyright (c) 1990, 1991, 1993
+.\" The Regents of the University of California. All rights reserved.
+.\"
+.\" This code is derived from software contributed to Berkeley by
+.\" Chris Torek and the American National Standards Committee X3,
+.\" on Information Processing Systems.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\" notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\" notice, this list of conditions and the following disclaimer in the
+.\" documentation and/or other materials provided with the distribution.
+.\" 3. All advertising materials mentioning features or use of this software
+.\" must display the following acknowledgement:
+.\" This product includes software developed by the University of
+.\" California, Berkeley and its contributors.
+.\" 4. Neither the name of the University nor the names of its contributors
+.\" may be used to endorse or promote products derived from this software
+.\" without specific prior written permission.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\" @(#)fseek.3 8.1 (Berkeley) 6/4/93
+.\" $FreeBSD: src/lib/libc/stdio/fseek.3,v 1.25 2004/03/20 08:38:27 tjr Exp $
+.\"
+.Dd March 19, 2004
+.Dt FSEEK 3
+.Os
+.Sh NAME
+.Nm fgetpos ,
+.Nm fseek ,
+.Nm fseeko ,
+.Nm fsetpos ,
+.Nm ftell ,
+.Nm ftello ,
+.Nm rewind
+.Nd reposition a stream
+.Sh LIBRARY
+.Lb libc
+.Sh SYNOPSIS
+.In stdio.h
+.Ft int
+.Fo fgetpos
+.Fa "FILE *restrict stream"
+.Fa "fpos_t *restrict pos"
+.Fc
+.Ft int
+.Fo fseek
+.Fa "FILE *stream"
+.Fa "long offset"
+.Fa "int whence"
+.Fc
+.Ft int
+.Fo fseeko
+.Fa "FILE *stream"
+.Fa "off_t offset"
+.Fa "int whence"
+.Fc
+.Ft int
+.Fo fsetpos
+.Fa "FILE *stream"
+.Fa "const fpos_t *pos"
+.Fc
+.Ft long
+.Fo ftell
+.Fa "FILE *stream"
+.Fc
+.Ft off_t
+.Fo ftello
+.Fa "FILE *stream"
+.Fc
+.Ft void
+.Fo rewind
+.Fa "FILE *stream"
+.Fc
+.Sh DESCRIPTION
+The
+.Fn fseek
+function sets the file position indicator for the stream pointed
+to by
+.Fa stream .
+The new position, measured in bytes, is obtained by adding
+.Fa offset
+bytes to the position specified by
+.Fa whence .
+If
+.Fa whence
+is set to
+.Dv SEEK_SET ,
+.Dv SEEK_CUR ,
+or
+.Dv 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
+.Fn fseek
+function clears the end-of-file indicator for the stream and undoes
+any effects of the
+.Xr ungetc 3
+and
+.Xr ungetwc 3
+functions on the same stream.
+.Pp
+The
+.Fn ftell
+function
+obtains the current value of the file position indicator for the
+stream pointed to by
+.Fa stream .
+.Pp
+The
+.Fn rewind
+function sets the file position indicator for the stream pointed
+to by
+.Fa stream
+to the beginning of the file.
+It is equivalent to:
+.Pp
+.Dl (void)fseek(stream, 0L, SEEK_SET)
+.Pp
+except that the error indicator for the stream is also cleared
+(see
+.Xr clearerr 3 ) .
+.Pp
+Since
+.Fn rewind
+does not return a value,
+an application wishing to detect errors should clear
+.Va errno ,
+then call
+.Fn rewind ,
+and if
+.Va errno
+is non-zero, assume an error has occurred.
+.Pp
+The
+.Fn fseeko
+function is identical to
+.Fn fseek ,
+except it takes an
+.Fa off_t
+argument
+instead of a
+.Fa long .
+Likewise, the
+.Fn ftello
+function is identical to
+.Fn ftell ,
+except it returns an
+.Fa off_t .
+.Pp
+The
+.Fn fgetpos
+and
+.Fn fsetpos
+functions
+are alternate interfaces for retrieving and setting the current position in
+the file, similar to
+.Fn ftell
+and
+.Fn fseek ,
+except that the current position is stored in an opaque object of
+type
+.Vt fpos_t
+pointed to by
+.Fa pos .
+These functions provide a portable way to seek to offsets larger than
+those that can be represented by a
+.Vt long int .
+They may also store additional state information in the
+.Vt fpos_t
+object to facilitate seeking within files containing multibyte
+characters with state-dependent encodings.
+Although
+.Vt 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.
+.Pp
+If the stream is a wide character stream (see
+.Xr fwide 3 ) ,
+the position specified by the combination of
+.Fa offset
+and
+.Fa whence
+must contain the first byte of a multibyte sequence.
+.Sh RETURN VALUES
+The
+.Fn rewind
+function
+returns no value.
+.Pp
+.Rv -std fgetpos fseek fseeko fsetpos
+.Pp
+Upon successful completion,
+.Fn ftell
+and
+.Fn ftello
+return the current offset.
+Otherwise, \-1 is returned and the global variable
+.Va errno
+is set to indicate the error.
+.Sh ERRORS
+.Bl -tag -width Er
+.It Bq Er EBADF
+The
+.Fa stream
+argument
+is not a seekable stream.
+.It Bq Er EINVAL
+The
+.Fa whence
+argument is invalid or
+the resulting file-position
+indicator would be set to a negative value.
+.It Bq Er EOVERFLOW
+The resulting file offset would be a value which
+cannot be represented correctly in an object of type
+.Fa off_t
+for
+.Fn fseeko
+and
+.Fn ftello
+or
+.Fa long
+for
+.Fn fseek
+and
+.Fn ftell .
+.It Bq Er ESPIPE
+The file descriptor underlying stream is associated with a pipe or FIFO
+or file-position indicator value is unspecified
+(see
+.Xr ungetc 3 ) .
+.El
+.Pp
+The functions
+.Fn fgetpos ,
+.Fn fseek ,
+.Fn fseeko ,
+.Fn fsetpos ,
+.Fn ftell ,
+and
+.Fn ftello
+may also fail and set
+.Va errno
+for any of the errors specified for the routines
+.Xr fflush 3 ,
+.Xr fstat 2 ,
+.Xr lseek 2 ,
+and
+.Xr malloc 3 .
+.Sh LEGACY SYNOPSIS
+.Fd #include <stdio.h>
+.Fd #include <sys/types.h>
+.Pp
+.Ft int
+.br
+.Fo fseeko
+.Fa "FILE *stream"
+.Fa "off_t offset"
+.Fa "int whence"
+.Fc ;
+.Pp
+The include file
+.In sys/types.h
+supplies the definition for
+.Vt off_t .
+.Sh SEE ALSO
+.Xr lseek 2 ,
+.Xr clearerr 3 ,
+.Xr fwide 3 ,
+.Xr ungetc 3 ,
+.Xr ungetwc 3 ,
+.Xr compat 5
+.Sh STANDARDS
+The
+.Fn fgetpos ,
+.Fn fsetpos ,
+.Fn fseek ,
+.Fn ftell ,
+and
+.Fn rewind
+functions
+conform to
+.St -isoC .
+.Pp
+The
+.Fn fseeko
+and
+.Fn ftello
+functions conform to
+.St -p1003.1-2001 .
projects / apple / libc.git / blobdiff