1.\" Copyright (c) 1983, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)truncate.2 8.1 (Berkeley) 6/4/93 33.\" $FreeBSD: src/lib/libc/sys/truncate.2,v 1.7.2.6 2001/12/14 18:34:02 ru Exp $ 34.\" $DragonFly: src/lib/libc/sys/truncate.2,v 1.3 2006/02/17 19:35:06 swildner Exp $ 35.\" 36.Dd June 4, 1993 37.Dt TRUNCATE 2 38.Os 39.Sh NAME 40.Nm truncate , 41.Nm ftruncate 42.Nd truncate or extend a file to a specified length 43.Sh LIBRARY 44.Lb libc 45.Sh SYNOPSIS 46.In unistd.h 47.Ft int 48.Fn truncate "const char *path" "off_t length" 49.Ft int 50.Fn ftruncate "int fd" "off_t length" 51.Sh DESCRIPTION 52.Fn Truncate 53causes the file named by 54.Fa path 55or referenced by 56.Fa fd 57to be truncated or extended to 58.Fa length 59bytes in size. If the file 60was larger than this size, the extra data 61is lost. 62If the file was smaller than this size, 63it will be extended as if by writing bytes 64with the value zero. 65With 66.Fn ftruncate , 67the file must be open for writing. 68.Sh RETURN VALUES 69.Rv -std 70.Sh ERRORS 71.Fn Truncate 72succeeds unless: 73.Bl -tag -width Er 74.It Bq Er ENOTDIR 75A component of the path prefix is not a directory. 76.It Bq Er ENAMETOOLONG 77A component of a pathname exceeded 255 characters, 78or an entire path name exceeded 1023 characters. 79.It Bq Er ENOENT 80The named file does not exist. 81.It Bq Er EACCES 82Search permission is denied for a component of the path prefix. 83.It Bq Er EACCES 84The named file is not writable by the user. 85.It Bq Er ELOOP 86Too many symbolic links were encountered in translating the pathname. 87.It Bq Er EISDIR 88The named file is a directory. 89.It Bq Er EROFS 90The named file resides on a read-only file system. 91.It Bq Er ETXTBSY 92The file is a pure procedure (shared text) file that is being executed. 93.It Bq Er EIO 94An I/O error occurred updating the inode. 95.It Bq Er EFAULT 96.Fa Path 97points outside the process's allocated address space. 98.El 99.Pp 100.Fn Ftruncate 101succeeds unless: 102.Bl -tag -width Er 103.It Bq Er EBADF 104The 105.Fa fd 106is not a valid descriptor. 107.It Bq Er EINVAL 108The 109.Fa fd 110references a socket, not a file. 111.It Bq Er EINVAL 112The 113.Fa fd 114is not open for writing. 115.El 116.Sh SEE ALSO 117.Xr open 2 118.Sh HISTORY 119The 120.Fn truncate 121function call appeared in 122.Bx 4.2 . 123.Sh BUGS 124These calls should be generalized to allow ranges 125of bytes in a file to be discarded. 126.Pp 127Use of 128.Fn truncate 129to extend a file is not portable. 130