1.\" $NetBSD: truncate.2,v 1.10 1999/12/02 21:42:40 kleink 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 39.Sh NAME 40.Nm truncate , 41.Nm ftruncate 42.Nd truncate a file to a specified length 43.Sh LIBRARY 44.Lb libc 45.Sh SYNOPSIS 46.Fd #include <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 to at most 58.Fa length 59bytes in size. If the file previously 60was larger than this size, the extra data 61is lost. 62With 63.Fn ftruncate , 64the file must be open for writing. 65.Sh RETURN VALUES 66A value of 0 is returned if the call succeeds. If the call 67fails a -1 is returned, and the global variable 68.Va errno 69specifies the error. 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 78.Dv {NAME_MAX} 79characters, or an entire path name exceeded 80.Dv {PATH_MAX} 81characters. 82.It Bq Er ENOENT 83The named file does not exist. 84.It Bq Er EACCES 85Search permission is denied for a component of the path prefix. 86.It Bq Er EACCES 87The named file is not writable by the user. 88.It Bq Er ELOOP 89Too many symbolic links were encountered in translating the pathname. 90.It Bq Er EISDIR 91The named file is a directory. 92.It Bq Er EROFS 93The named file resides on a read-only file system. 94.It Bq Er ETXTBSY 95The file is a pure procedure (shared text) file that is being executed. 96.It Bq Er EIO 97An I/O error occurred updating the inode. 98.It Bq Er EFAULT 99.Fa path 100points outside the process's allocated address space. 101.El 102.Pp 103.Fn ftruncate 104succeeds unless: 105.Bl -tag -width Er 106.It Bq Er EBADF 107The 108.Fa fd 109is not a valid descriptor. 110.It Bq Er EINVAL 111The 112.Fa fd 113references a socket, not a file. 114.It Bq Er EINVAL 115The 116.Fa fd 117is not open for writing. 118.El 119.Sh SEE ALSO 120.Xr open 2 121.Sh BUGS 122These calls should be generalized to allow ranges 123of bytes in a file to be discarded. 124.Sh HISTORY 125The 126.Fn truncate 127and 128.Fn ftruncate 129function calls appeared in 130.Bx 4.2 . 131