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 1.2 1993/08/01 07:42:06 mycroft 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 [ENOTDIR] 70.It Bq Er ENOTDIR 71A component of the path prefix is not a directory. 72.It Bq Er EINVAL 73The pathname contains a character with the high-order bit set. 74.It Bq Er ENAMETOOLONG 75A component of a pathname exceeded 255 characters, 76or an entire path name exceeded 1023 characters. 77.It Bq Er ENOENT 78The named file does not exist. 79.It Bq Er EACCES 80Search permission is denied for a component of the path prefix. 81.It Bq Er EACCES 82The named file is not writable by the user. 83.It Bq Er ELOOP 84Too many symbolic links were encountered in translating the pathname. 85.It Bq Er EISDIR 86The named file is a directory. 87.It Bq Er EROFS 88The named file resides on a read-only file system. 89.It Bq Er ETXTBSY 90The file is a pure procedure (shared text) file that is being executed. 91.It Bq Er EIO 92An I/O error occurred updating the inode. 93.It Bq Er EFAULT 94.Fa Path 95points outside the process's allocated address space. 96.El 97.Pp 98.Fn Ftruncate 99succeeds unless: 100.Bl -tag -width [ENOTDIR] 101.It Bq Er EBADF 102The 103.Fa fd 104is not a valid descriptor. 105.It Bq Er EINVAL 106The 107.Fa fd 108references a socket, not a file. 109.It Bq Er EINVAL 110The 111.Fa fd 112is not open for writing. 113.El 114.Sh SEE ALSO 115.Xr open 2 116.Sh BUGS 117These calls should be generalized to allow ranges 118of bytes in a file to be discarded. 119.Sh HISTORY 120The 121.Nm 122function call appeared in 123.Bx 4.2 . 124