1.\" Copyright (c) 1980, 1991, 1993 2.\" The Regents of the University of California. 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. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)open.2 8.2 (Berkeley) 11/16/93 29.\" 30.Dd March 30, 2020 31.Dt POSIX_FALLOCATE 2 32.Os 33.Sh NAME 34.Nm posix_fallocate 35.Nd pre-allocate storage for a range in a file 36.Sh LIBRARY 37.Lb libc 38.Sh SYNOPSIS 39.In fcntl.h 40.Ft int 41.Fn posix_fallocate "int fd" "off_t offset" "off_t len" 42.Sh DESCRIPTION 43Required storage for the range 44.Fa offset 45to 46.Fa offset + 47.Fa len 48in the file referenced by 49.Fa fd 50is guaranteed to be allocated upon successful return. 51That is, if 52.Fn posix_fallocate 53returns successfully, subsequent writes to the specified file data 54will not fail due to lack of free space on the file system storage 55media. 56Any existing file data in the specified range is unmodified. 57If 58.Fa offset + 59.Fa len 60is beyond the current file size, then 61.Fn posix_fallocate 62will adjust the file size to 63.Fa offset + 64.Fa len . 65Otherwise, the file size will not be changed. 66.Pp 67Space allocated by 68.Fn posix_fallocate 69will be freed by a successful call to 70.Xr creat 2 71or 72.Xr open 2 73that truncates the size of the file. 74Space allocated via 75.Fn posix_fallocate 76may be freed by a successful call to 77.Xr ftruncate 2 78that reduces the file size to a size smaller than 79.Fa offset + 80.Fa len . 81.Sh RETURN VALUES 82If successful, 83.Fn posix_fallocate 84returns zero. 85It returns an error on failure, without setting 86.Va errno . 87.Sh ERRORS 88Possible failure conditions: 89.Bl -tag -width Er 90.It Bq Er EBADF 91The 92.Fa fd 93argument is not a valid file descriptor. 94.It Bq Er EBADF 95The 96.Fa fd 97argument references a file that was opened without write permission. 98.It Bq Er EFBIG 99The value of 100.Fa offset + 101.Fa len 102is greater than the maximum file size. 103.It Bq Er EINTR 104A signal was caught during execution. 105.It Bq Er EINVAL 106The 107.Fa len 108argument was less than or equal to zero, the 109.Fa offset 110argument was less than zero, 111or the operation is not supported by the file system. 112.It Bq Er EIO 113An I/O error occurred while reading from or writing to a file system. 114.It Bq Er EINTEGRITY 115Corrupted data was detected while reading from the file system. 116.It Bq Er ENODEV 117The 118.Fa fd 119argument does not refer to a file that supports 120.Nm . 121.It Bq Er ENOSPC 122There is insufficient free space remaining on the file system storage 123media. 124.It Bq Er ENOTCAPABLE 125The file descriptor 126.Fa fd 127has insufficient rights. 128.It Bq Er ESPIPE 129The 130.Fa fd 131argument is associated with a pipe or FIFO. 132.El 133.Sh SEE ALSO 134.Xr creat 2 , 135.Xr ftruncate 2 , 136.Xr open 2 , 137.Xr unlink 2 138.Sh STANDARDS 139The 140.Fn posix_fallocate 141system call conforms to 142.St -p1003.1-2004 . 143.Sh HISTORY 144The 145.Fn posix_fallocate 146function appeared in 147.Fx 9.0 . 148.Sh AUTHORS 149.Fn posix_fallocate 150and this manual page were initially written by 151.An Matthew Fleming Aq Mt [email protected] . 152