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+.\" 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.
+.\" 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.
+.\"
+.\"     @(#)truncate.2	8.1 (Berkeley) 6/4/93
+.\" $FreeBSD$
+.\"
+.Dd December 13, 2006
+.Dt TRUNCATE 2
+.Os
+.Sh NAME
+.Nm truncate ,
+.Nm ftruncate
+.Nd truncate or extend 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
+The
+.Fn truncate
+system call
+causes the file named by
+.Fa path
+or referenced by
+.Fa fd
+to be truncated or extended to
+.Fa length
+bytes in size.
+If the file
+was larger than this size, the extra data
+is lost.
+If the file was smaller than this size,
+it will be extended as if by writing bytes
+with the value zero.
+With
+.Fn ftruncate ,
+the file must be open for writing.
+.Sh RETURN VALUES
+.Rv -std
+If the file to be modified is not a directory or
+a regular file, the
+.Fn truncate
+call has no effect and returns the value 0.
+.Sh ERRORS
+The
+.Fn truncate
+system call
+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 255 characters,
+or an entire path name exceeded 1023 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.
+.It Bq Er EACCES
+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 EPERM
+The named file has its immutable or append-only flag set, see the
+.Xr chflags 2
+manual page for more information.
+.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 EFBIG
+The
+.Fa length
+argument was greater than the maximum file size.
+.It Bq Er EINVAL
+The
+.Fa length
+argument was less than 0.
+.It Bq Er EIO
+An I/O error occurred updating the inode.
+.It Bq Er EFAULT
+The
+.Fa path
+argument
+points outside the process's allocated address space.
+.El
+.Pp
+The
+.Fn ftruncate
+system call
+succeeds unless:
+.Bl -tag -width Er
+.It Bq Er EBADF
+The
+.Fa fd
+argument
+is not a valid descriptor.
+.It Bq Er EINVAL
+The
+.Fa fd
+argument
+references a socket, not a file.
+.It Bq Er EINVAL
+The
+.Fa fd
+descriptor
+is not open for writing.
+.El
+.Sh SEE ALSO
+.Xr chflags 2 ,
+.Xr open 2
+.Sh HISTORY
+The
+.Fn truncate
+system call 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.