.\" Copyright (c) 1983, 1991, 1993.\"	The Regents of the University of California.  All rights reserved..\".\" Redistribution and use in source and binary forms, with or without.\" modification, are permitted provided that the following conditions.\" are met:.\" 1. Redistributions of source code must retain the above copyright.\"    notice, this list of conditions and the following disclaimer..\" 2. Redistributions in binary form must reproduce the above copyright.\"    notice, this list of conditions and the following disclaimer in the.\"    documentation and/or other materials provided with the distribution..\" 3. All advertising materials mentioning features or use of this software.\"    must display the following acknowledgement:.\"	This product includes software developed by the University of.\"	California, Berkeley and its contributors..\" 4. Neither the name of the University nor the names of its contributors.\"    may be used to endorse or promote products derived from this software.\"    without specific prior written permission..\".\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION).\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF.\" SUCH DAMAGE..\".\"     @(#)truncate.2	8.1 (Berkeley) 6/4/93.\".Dd June 4, 1993.Dt TRUNCATE 2.Os BSD 4.2.Sh NAME.Nm truncate ,.Nm ftruncate.Nd truncate a file to a specified length.Sh SYNOPSIS.Fd #include <unistd.h>.Ft int.Fn truncate "const char *path" "off_t length".Ft int.Fn ftruncate "int fd" "off_t length".Sh DESCRIPTION.Fn Truncatecauses the file named by.Fa pathor referenced by.Fa fdto be truncated to at most.Fa lengthbytes in size.  If the file previouslywas larger than this size, the extra datais lost.With.Fn ftruncate ,the file must be open for writing..Sh RETURN VALUESA value of 0 is returned if the call succeeds.  If the callfails a -1 is returned, and the global variable.Va errnospecifies the error..Sh ERRORS.Fn Truncatesucceeds unless:.Bl -tag -width [ENOTDIR].It Bq Er ENOTDIRA component of the path prefix is not a directory..It Bq Er EINVALThe pathname contains a character with the high-order bit set..It Bq Er ENAMETOOLONGA component of a pathname exceeded 255 characters,or an entire path name exceeded 1023 characters..It Bq Er ENOENTThe named file does not exist..It Bq Er EACCESSearch permission is denied for a component of the path prefix..It Bq Er EACCESThe named file is not writable by the user..It Bq Er ELOOPToo many symbolic links were encountered in translating the pathname..It Bq Er EISDIRThe named file is a directory..It Bq Er EROFSThe named file resides on a read-only file system..It Bq Er ETXTBSYThe file is a pure procedure (shared text) file that is being executed..It Bq Er EIOAn I/O error occurred updating the inode..It Bq Er EFAULT.Fa Pathpoints outside the process's allocated address space..El.Pp.Fn Ftruncatesucceeds unless:.Bl -tag -width [ENOTDIR].It Bq Er EBADFThe.Fa fdis not a valid descriptor..It Bq Er EINVALThe.Fa fdreferences a socket, not a file..It Bq Er EINVALThe.Fa fdis not open for writing..El.Sh SEE ALSO.Xr open 2.Sh BUGSThese calls should be generalized to allow rangesof bytes in a file to be discarded..Sh HISTORYThe.Nmfunction call appeared in.Bx 4.2 .