1.\" Copyright (c) 1983, 1991 The Regents of the University of California. 2.\" 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.\" from: @(#)truncate.2 6.9 (Berkeley) 3/10/91 33.\" $Id: truncate.2,v 1.6 1994/04/22 00:13:53 jtc Exp $ 34.\" 35.Dd March 10, 1991 36.Dt TRUNCATE 2 37.Os BSD 4.2 38.Sh NAME 39.Nm truncate 40.Nd truncate a file to a specified length 41.Sh SYNOPSIS 42.Fd #include <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 to at most 54.Fa length 55bytes in size. If the file previously 56was larger than this size, the extra data 57is lost. 58With 59.Fn ftruncate , 60the file must be open for writing. 61.Sh RETURN VALUES 62A value of 0 is returned if the call succeeds. If the call 63fails a -1 is returned, and the global variable 64.Va errno 65specifies the error. 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 74.Dv {NAME_MAX} 75characters, or an entire path name exceeded 76.Dv {PATH_MAX} 77characters. 78.It Bq Er ENOENT 79The named file does not exist. 80.It Bq Er EACCES 81Search permission is denied for a component of the path prefix. 82.It Bq Er EACCES 83The named file is not writable by the user. 84.It Bq Er ELOOP 85Too many symbolic links were encountered in translating the pathname. 86.It Bq Er EISDIR 87The named file is a directory. 88.It Bq Er EROFS 89The named file resides on a read-only file system. 90.It Bq Er ETXTBSY 91The file is a pure procedure (shared text) file that is being executed. 92.It Bq Er EIO 93An I/O error occurred updating the inode. 94.It Bq Er EFAULT 95.Fa Path 96points outside the process's allocated address space. 97.El 98.Pp 99.Fn Ftruncate 100succeeds unless: 101.Bl -tag -width Er 102.It Bq Er EBADF 103The 104.Fa fd 105is not a valid descriptor. 106.It Bq Er EINVAL 107The 108.Fa fd 109references a socket, not a file. 110.It Bq Er EINVAL 111The 112.Fa fd 113is not open for writing. 114.El 115.Sh SEE ALSO 116.Xr open 2 117.Sh BUGS 118These calls should be generalized to allow ranges 119of bytes in a file to be discarded. 120.Sh HISTORY 121The 122.Fn truncate 123and 124.Fn ftruncate 125function calls appeared in 126.Bx 4.2 . 127