135 lines
3.9 KiB
Groff
135 lines
3.9 KiB
Groff
.\" $NetBSD: truncate.2,v 1.21 2004/05/13 10:20:58 wiz Exp $
|
|
.\"
|
|
.\" Copyright (c) 1983, 1991, 1993
|
|
.\" The Regents of the University of California. All rights reserved.
|
|
.\"
|
|
.\" 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. 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.
|
|
.\"
|
|
.\" @(#)truncate.2 8.1 (Berkeley) 6/4/93
|
|
.\"
|
|
.Dd August 18, 2002
|
|
.Dt TRUNCATE 2
|
|
.Os
|
|
.Sh NAME
|
|
.Nm truncate ,
|
|
.Nm ftruncate
|
|
.Nd truncate a file to a specified length
|
|
.Sh LIBRARY
|
|
.Lb libc
|
|
.Sh SYNOPSIS
|
|
.In unistd.h
|
|
.Ft int
|
|
.Fn truncate "const char *path" "off_t length"
|
|
.Ft int
|
|
.Fn ftruncate "int fd" "off_t length"
|
|
.Sh DESCRIPTION
|
|
.Fn truncate
|
|
causes the file named by
|
|
.Fa path
|
|
or referenced by
|
|
.Fa fd
|
|
to have a size of
|
|
.Fa length
|
|
bytes.
|
|
If the file previously was larger than this size, the extra data is discarded.
|
|
If it was previously shorter than
|
|
.Fa length ,
|
|
its size is increased to the specified value and
|
|
the extended area appears as if it were zero-filled.
|
|
.Pp
|
|
With
|
|
.Fn ftruncate ,
|
|
the file must be open for writing; for
|
|
.Fn truncate ,
|
|
the process must have write permissions for the file.
|
|
.Sh RETURN VALUES
|
|
A value of 0 is returned if the call succeeds.
|
|
If the call fails a \-1 is returned, and the global variable
|
|
.Va errno
|
|
specifies the error.
|
|
.Sh ERRORS
|
|
.Fn truncate
|
|
succeeds unless:
|
|
.Bl -tag -width Er
|
|
.It Bq Er ENOTDIR
|
|
A component of the path prefix is not a directory.
|
|
.It Bq Er ENAMETOOLONG
|
|
A component of a pathname exceeded
|
|
.Dv {NAME_MAX}
|
|
characters, or an entire path name exceeded
|
|
.Dv {PATH_MAX}
|
|
characters.
|
|
.It Bq Er ENOENT
|
|
The named file does not exist.
|
|
.It Bq Er EACCES
|
|
Search permission is denied for a component of the path prefix, or
|
|
the named file is not writable by the user.
|
|
.It Bq Er ELOOP
|
|
Too many symbolic links were encountered in translating the pathname.
|
|
.It Bq Er EISDIR
|
|
The named file is a directory.
|
|
.It Bq Er EROFS
|
|
The named file resides on a read-only file system.
|
|
.It Bq Er ETXTBSY
|
|
The file is a pure procedure (shared text) file that is being executed.
|
|
.It Bq Er EIO
|
|
An I/O error occurred updating the inode.
|
|
.It Bq Er EFAULT
|
|
.Fa path
|
|
points outside the process's allocated address space.
|
|
.El
|
|
.Pp
|
|
.Fn ftruncate
|
|
succeeds unless:
|
|
.Bl -tag -width Er
|
|
.It Bq Er EBADF
|
|
The
|
|
.Fa fd
|
|
is not a valid descriptor.
|
|
.It Bq Er EINVAL
|
|
The
|
|
.Fa fd
|
|
references a socket, not a file, or
|
|
the
|
|
.Fa fd
|
|
is not open for writing.
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr open 2
|
|
.Sh HISTORY
|
|
The
|
|
.Fn truncate
|
|
and
|
|
.Fn ftruncate
|
|
function calls appeared in
|
|
.Bx 4.2 .
|
|
.Sh BUGS
|
|
These calls should be generalized to allow ranges
|
|
of bytes in a file to be discarded.
|
|
.Pp
|
|
Use of
|
|
.Fn truncate
|
|
to extend a file is not portable.
|