1.\" $NetBSD: truncate.2,v 1.7 1995/02/27 12:39:00 cgd Exp $ 2.\" 3.\" Copyright (c) 1983, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" @(#)truncate.2 8.1 (Berkeley) 6/4/93 35.\" 36.Dd June 4, 1993 37.Dt TRUNCATE 2 38.Os BSD 4.2 39.Sh NAME 40.Nm truncate , 41.Nm ftruncate 42.Nd truncate a file to a specified length 43.Sh SYNOPSIS 44.Fd #include <unistd.h> 45.Ft int 46.Fn truncate "const char *path" "off_t length" 47.Ft int 48.Fn ftruncate "int fd" "off_t length" 49.Sh DESCRIPTION 50.Fn Truncate 51causes the file named by 52.Fa path 53or referenced by 54.Fa fd 55to be truncated to at most 56.Fa length 57bytes in size. If the file previously 58was larger than this size, the extra data 59is lost. 60With 61.Fn ftruncate , 62the file must be open for writing. 63.Sh RETURN VALUES 64A value of 0 is returned if the call succeeds. If the call 65fails a -1 is returned, and the global variable 66.Va errno 67specifies the error. 68.Sh ERRORS 69.Fn Truncate 70succeeds unless: 71.Bl -tag -width Er 72.It Bq Er ENOTDIR 73A component of the path prefix is not a directory. 74.It Bq Er ENAMETOOLONG 75A component of a pathname exceeded 76.Dv {NAME_MAX} 77characters, or an entire path name exceeded 78.Dv {PATH_MAX} 79characters. 80.It Bq Er ENOENT 81The named file does not exist. 82.It Bq Er EACCES 83Search permission is denied for a component of the path prefix. 84.It Bq Er EACCES 85The named file is not writable by the user. 86.It Bq Er ELOOP 87Too many symbolic links were encountered in translating the pathname. 88.It Bq Er EISDIR 89The named file is a directory. 90.It Bq Er EROFS 91The named file resides on a read-only file system. 92.It Bq Er ETXTBSY 93The file is a pure procedure (shared text) file that is being executed. 94.It Bq Er EIO 95An I/O error occurred updating the inode. 96.It Bq Er EFAULT 97.Fa Path 98points outside the process's allocated address space. 99.El 100.Pp 101.Fn Ftruncate 102succeeds unless: 103.Bl -tag -width Er 104.It Bq Er EBADF 105The 106.Fa fd 107is not a valid descriptor. 108.It Bq Er EINVAL 109The 110.Fa fd 111references a socket, not a file. 112.It Bq Er EINVAL 113The 114.Fa fd 115is not open for writing. 116.El 117.Sh SEE ALSO 118.Xr open 2 119.Sh BUGS 120These calls should be generalized to allow ranges 121of bytes in a file to be discarded. 122.Sh HISTORY 123The 124.Fn truncate 125and 126.Fn ftruncate 127function calls appeared in 128.Bx 4.2 . 129