<!-- Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009, 2013 The President and Fellows of Harvard College. 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. 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 UNIVERSITY 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 UNIVERSITY 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. --> <html> <head> <title>ftruncate</title> <body bgcolor=#ffffff> <h2 align=center>ftruncate</h2> <h4 align=center>OS/161 Reference Manual</h4> <h3>Name</h3> <p> ftruncate - set size of a file </p> <h3>Library</h3> <p> Standard C Library (libc, -lc) </p> <h3>Synopsis</h3> <p> <tt>#include <unistd.h></tt><br> <br> <tt>int</tt><br> <tt>ftruncate(int </tt><em>fd</em><tt>, off_t </tt><em>filesize</em><tt>);</tt> </p> <h3>Description</h3> <p> <tt>ftruncate</tt> forcibly sets the size of the file referred to by <em>fd</em> to <em>filesize</em>. If this expands the file, the new data appears as if it is zero-filled. (On file systems that support sparse files, the new space does not need to be physically allocated.) If the action shrinks the file, the excess data is discarded. </p> <p> The file must be open for write. </p> <p> <tt>ftruncate</tt> must be atomic. For recoverable file systems, this includes after crashing and running recovery. </p> <h3>Return Values</h3> <p> On success, <tt>ftruncate</tt> returns 0. On error, -1 is returned, and <A HREF=errno.html>errno</A> is set according to the error encountered. </p> <h3>Errors</h3> <p> The following error codes should be returned under the conditions given. Other error codes may be returned for other cases not mentioned here. <table width=90%> <tr><td width=5% rowspan=3> </td> <td width=10% valign=top>EBADF</td> <td><em>fd</em> is not a valid file handle, or it is not open for writing.</td></tr> <tr><td valign=top>EIO</td> <td>A hard I/O error occurred.</td></tr> <tr><td valign=top>EFAULT</td> <td><em>buf</em> points to an invalid address.</td></tr> </table> </p> </body> </html>