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