1.\" Copyright (c) 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.\" @(#)getbsize.3 8.1 (Berkeley) 6/4/93 29.\" $FreeBSD$ 30.\" 31.Dd June 11, 2017 32.Dt GETBSIZE 3 33.Os 34.Sh NAME 35.Nm getbsize 36.Nd get preferred block size 37.Sh LIBRARY 38.Lb libc 39.Sh SYNOPSIS 40.In stdlib.h 41.Ft char * 42.Fn getbsize "int *headerlenp" "long *blocksizep" 43.Sh DESCRIPTION 44The 45.Fn getbsize 46function returns a preferred block size for reporting by system utilities 47.Xr df 1 , 48.Xr du 1 , 49.Xr ls 1 50and 51.Xr systat 1 , 52based on the value of the 53.Ev BLOCKSIZE 54environment variable. 55.Ev BLOCKSIZE 56may be specified directly in bytes, or in multiples of a kilobyte by 57specifying a number followed by ``K'' or ``k'', in multiples of a 58megabyte by specifying a number followed by ``M'' or ``m'' or in 59multiples of a gigabyte by specifying a number followed by ``G'' or 60``g''. 61Multiples must be integers. 62.Pp 63Valid values of 64.Ev BLOCKSIZE 65are 512 bytes to 1 gigabyte. 66Sizes less than 512 bytes are rounded up to 512 bytes, and sizes 67greater than 1 GB are rounded down to 1 GB. 68In each case 69.Fn getbsize 70produces a warning message via 71.Xr warnx 3 . 72.Pp 73The 74.Fn getbsize 75function returns a pointer to a null-terminated string describing 76the block size, something like 77.Dq 1K-blocks . 78The memory referenced by 79.Fa headerlenp 80is filled in with the length of the string (not including the 81terminating null). 82The memory referenced by 83.Fa blocksizep 84is filled in with block size, in bytes. 85.Sh SEE ALSO 86.Xr df 1 , 87.Xr du 1 , 88.Xr ls 1 , 89.Xr systat 1 , 90.Xr environ 7 91.Sh HISTORY 92The 93.Fn getbsize 94function first appeared in 95.Bx 4.4 . 96