BSD 4_3_Net_2 release

[unix-history] / usr / src / lib / libc / sys / lseek.2

diff --git a/usr/src/lib/libc/sys/lseek.2 b/usr/src/lib/libc/sys/lseek.2
index 2105314..f6d8e88 100644 (file)
--- a/usr/src/lib/libc/sys/lseek.2
+++ b/usr/src/lib/libc/sys/lseek.2
@@ -1,74 +1,135 @@
-.\" Copyright (c) 1980 Regents of the University of California.
-.\" All rights reserved.  The Berkeley software License Agreement
-.\" specifies the terms and conditions for redistribution.
+.\" Copyright (c) 1980, 1991 Regents of the University of California.
+.\" All rights reserved.

 .\"
 .\"

-.\"    @(#)lseek.2     4.1 (Berkeley) %G%
+.\" 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.

 .\"
 .\"

-.TH LSEEK 2 
-.UC 4
-.SH NAME
-lseek, tell \- move read/write pointer
-.SH SYNOPSIS
-.nf
-.B long lseek(fildes, offset, whence)
-.B long offset;
-.PP
-.B long tell(fildes)
-.fi
-.SH DESCRIPTION
-The file
-descriptor refers to a file open for reading or writing.
-The read (resp. write) pointer for the file is set as follows:
-.IP
+.\" 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.
+.\"
+.\"     @(#)lseek.2    6.5 (Berkeley) 3/10/91
+.\"
+.Dd March 10, 1991
+.Dt LSEEK 2
+.Os BSD 4
+.Sh NAME
+.Nm lseek
+.Nd reposition read/write file offset
+.Sh SYNOPSIS
+.Fd #include <unistd.h>
+.Ft off_t
+.Fn lseek "int fildes" "off_t offset" "int whence"
+.Sh DESCRIPTION
+The
+.Fn lseek
+function repositions the offset of the file descriptor
+.Fa fildes
+to the
+argument
+.Fa offset
+according to the directive
+.Fa whence.
+The argument
+.Fa fildes
+must be an open
+file descriptor.
+.Fn Lseek
+repositions the file pointer
+.Fa fildes
+as follows:
+.Bl -item -offset indent
+.It

 If
 If

-.I whence
-is 0, the pointer is set to
-.I offset
+.Fa whence
+is
+.Dv SEEK_SET ,
+the offset is set to
+.Fa offset

 bytes.
 bytes.

-.IP
+.It

 If
 If

-.I whence
-is 1, the pointer is set to its current location plus
-.IR offset .
-.IP
+.Fa whence
+is
+.Dv SEEK_CUR ,
+the offset is set to its current location plus
+.Fa offset
+bytes.
+.It

 If
 If

-.I whence
-is 2, the pointer is set to the size of the
+.Fa whence
+is
+.Dv SEEK_END ,
+the offset is set to the size of the

 file plus
 file plus

-.IR offset .
-.PP
-The returned value is the resulting pointer location.
-.PP
-The obsolete function
-.IR tell ( fildes )
-is identical to
-.IR lseek ( "fildes, 0L, 1" ).
-.PP
-Seeking far beyond the end of a file, then writing,
-creates a gap or `hole', which occupies no
-physical space and reads as zeros.
-.SH "SEE ALSO"
-open(2), creat(2), fseek(3)
-.SH DIAGNOSTICS
-\-1
-is returned for
-an undefined file descriptor,
-seek on a pipe,
-or seek to a position before the beginning of file.
-.SH BUGS
-.I Lseek
-is a no-op on character special files.
-.SH "ASSEMBLER (PDP-11)"
-(lseek = 19.)
-.br
-(file descriptor in r0)
-.br
-.B sys lseek; offset1; offset2; whence
-.PP
-.I Offset1
-and
-.I offset2
-are the high and low words of 
-.IR offset ;
-r0 and r1 contain
-the pointer upon return.
+.Fa offset
+bytes.
+.El
+.Pp
+The
+.Fn lseek
+function allows the file offset to be set beyond the end
+of the existing end-of-file of the file. If data is later written
+at this point, subsequent reads of the data in the gap return
+bytes of zeros (until data is actualy written into the gap).
+.Pp
+Some devices are incapable of seeking.  The value of the pointer
+associated with such a device is undefined.
+.Sh RETURN VALUES
+Upon successful completion,
+.Fn lseek
+returns the resulting offset location as measured in bytes from the
+begining of the file.
+Otherwise,
+a value of -1 is returned and
+.Va errno
+is set to indicate
+the error.
+.Sh ERRORS
+.Fn Lseek
+will fail and the file pointer will remain unchanged if:
+.Bl -tag -width [EINVAL]
+.It Bq Er EBADF
+.Em Fildes
+is not an open file descriptor.
+.It Bq Er ESPIPE
+.Em Fildes
+is associated with a pipe, socket, or FIFO.
+.It Bq Er EINVAL
+.Fa Whence
+is not a proper value.
+.El
+.Sh SEE ALSO
+.Xr dup 2 ,
+.Xr open 2
+.Sh BUGS
+This document's use of
+.Fa whence
+is incorrect English, but maintained for historical reasons.
+.Sh STANDARDS
+The
+.Fn lseek
+function
+conforms to IEEE Std 1003.1-1988
+.Pq Dq Tn POSIX .