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