freebsd/lib/libc/sys/truncate.2

.\" 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.
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.\" 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`
$Id$ -> $FreeBSD$ 1999-08-28 00:22:10 +00:00			`.\" $FreeBSD$`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.\"`
- truncate(2) returns EFBIG if the length argument was greater than the maximum file size. - truncate(2) returns EINVAL if the length argument was less than 0. 2006-12-13 22:51:23 +00:00			`.Dd December 13, 2006`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Dt TRUNCATE 2`
mdoc(7) police: removed HISTORY info from the .Os call. 2001-07-10 13:41:46 +00:00			`.Os`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Sh NAME`
			`.Nm truncate ,`
			`.Nm ftruncate`
Document that truncate can also be used to extend the size of a file, but doing so is not truly portable. 1996-06-07 01:34:47 +00:00			`.Nd truncate or extend a file to a specified length`
Introduce ".Lb" macro to libc manpages. More libraries manpages updates following. 2000-04-21 09:42:15 +00:00			`.Sh LIBRARY`
			`.Lb libc`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Sh SYNOPSIS`
mdoc(7) police: Use the new .In macro for #include statements. 2001-10-01 16:09:29 +00:00			`.In unistd.h`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Ft int`
			`.Fn truncate "const char *path" "off_t length"`
			`.Ft int`
			`.Fn ftruncate "int fd" "off_t length"`
			`.Sh DESCRIPTION`
mdoc(7) police: Tidy up the syscall language. Stop calling system calls "function calls". Use "The .Fn system call" a-la "The .Nm utility". When referring to a non-BSD implementation in the HISTORY section, call syscall a function, to be safe. 2002-12-18 09:22:32 +00:00			`The`
			`.Fn truncate`
			`system call`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`causes the file named by`
			`.Fa path`
			`or referenced by`
			`.Fa fd`
Document that truncate can also be used to extend the size of a file, but doing so is not truly portable. 1996-06-07 01:34:47 +00:00			`to be truncated or extended to`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Fa length`
Mechanically kill hard sentence breaks. 2004-07-02 23:52:20 +00:00			`bytes in size.`
			`If the file`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`was larger than this size, the extra data`
			`is lost.`
Document that truncate can also be used to extend the size of a file, but doing so is not truly portable. 1996-06-07 01:34:47 +00:00			`If the file was smaller than this size,`
Rephrase some things as suggested by Bruce. 1996-06-08 15:59:43 +00:00			`it will be extended as if by writing bytes`
			`with the value zero.`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`With`
			`.Fn ftruncate ,`
			`the file must be open for writing.`
			`.Sh RETURN VALUES`
Use ``.Rv -std'' wherever possible. Submitted by: yar 2001-08-31 09:57:38 +00:00			`.Rv -std`
o Document the fact truncate(2) has no effect for !VDIR or !VREG files. Submitted by: ceri 2006-06-01 14:20:43 +00:00			`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.`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Sh ERRORS`
mdoc(7) police: Tidy up the syscall language. Stop calling system calls "function calls". Use "The .Fn system call" a-la "The .Nm utility". When referring to a non-BSD implementation in the HISTORY section, call syscall a function, to be safe. 2002-12-18 09:22:32 +00:00			`The`
			`.Fn truncate`
			`system call`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`succeeds unless:`
Use `Er' variable to define first column width in ERRORS section. It was initially suggested by mdoc(7) style, but was broken over the years 2000-05-04 13:09:25 +00:00			`.Bl -tag -width Er`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.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.`
If the named file has its immutable or append-only flag set, truncate(2) and ftruncate(2) return EPERM. Note, that if the append-only flag is set even increasing size of the file is not permitted. 2006-12-09 22:49:28 +00:00			`.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.`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.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.`
- truncate(2) returns EFBIG if the length argument was greater than the maximum file size. - truncate(2) returns EINVAL if the length argument was less than 0. 2006-12-13 22:51:23 +00:00			`.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.`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.It Bq Er EIO`
			`An I/O error occurred updating the inode.`
			`.It Bq Er EFAULT`
mdoc(7) police: "The .Fa argument.". 2002-12-19 09:40:28 +00:00			`The`
			`.Fa path`
			`argument`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`points outside the process's allocated address space.`
			`.El`
			`.Pp`
mdoc(7) police: Tidy up the syscall language. Stop calling system calls "function calls". Use "The .Fn system call" a-la "The .Nm utility". When referring to a non-BSD implementation in the HISTORY section, call syscall a function, to be safe. 2002-12-18 09:22:32 +00:00			`The`
			`.Fn ftruncate`
			`system call`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`succeeds unless:`
mdoc(7) police: Er macro usage cleanup. 2000-11-22 16:02:00 +00:00			`.Bl -tag -width Er`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.It Bq Er EBADF`
			`The`
			`.Fa fd`
mdoc(7) police: "The .Fa argument.". 2002-12-19 09:40:28 +00:00			`argument`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`is not a valid descriptor.`
			`.It Bq Er EINVAL`
			`The`
			`.Fa fd`
mdoc(7) police: "The .Fa argument.". 2002-12-19 09:40:28 +00:00			`argument`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`references a socket, not a file.`
			`.It Bq Er EINVAL`
			`The`
			`.Fa fd`
mdoc(7) police: "The .Fa argument.". 2002-12-19 09:40:28 +00:00			`descriptor`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`is not open for writing.`
			`.El`
			`.Sh SEE ALSO`
If the named file has its immutable or append-only flag set, truncate(2) and ftruncate(2) return EPERM. Note, that if the append-only flag is set even increasing size of the file is not permitted. 2006-12-09 22:49:28 +00:00			`.Xr chflags 2 ,`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Xr open 2`
Sort sections. 2005-01-20 09:17:07 +00:00			`.Sh HISTORY`
			`The`
			`.Fn truncate`
			`system call appeared in`
			`.Bx 4.2 .`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Sh BUGS`
			`These calls should be generalized to allow ranges`
			`of bytes in a file to be discarded.`
Document that truncate can also be used to extend the size of a file, but doing so is not truly portable. 1996-06-07 01:34:47 +00:00			`.Pp`
			`Use of`
			`.Fn truncate`
			`to extend a file is not portable.`