2004-11-03 13:51:07 +00:00
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.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
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2007-06-20 22:33:04 +00:00
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.TH "DF" 1P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
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2004-11-03 13:51:07 +00:00
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.\" df
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2007-09-20 06:03:25 +00:00
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.SH PROLOG
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This manual page is part of the POSIX Programmer's Manual.
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The Linux implementation of this interface may differ (consult
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the corresponding Linux manual page for details of Linux behavior),
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or the interface may not be implemented on Linux.
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2004-11-03 13:51:07 +00:00
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.SH NAME
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df \- report free disk space
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.SH SYNOPSIS
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.LP
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\fBdf\fP \fB[\fP\fB-k\fP\fB][\fP\fB-P|-t\fP\fB][\fP\fIfile\fP\fB...\fP\fB]\fP\fB\fP
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.SH DESCRIPTION
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.LP
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2007-11-18 06:52:48 +00:00
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The \fIdf\fP utility shall write the amount of available space and
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2004-11-03 13:51:07 +00:00
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file slots for file systems on which the invoking user has appropriate
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read access. File systems shall be specified
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by the \fIfile\fP operands; when none are specified, information shall
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be written for all file systems. The format of the default
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output from \fIdf\fP is unspecified, but all space figures are reported
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in 512-byte units, unless the \fB-k\fP option is
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specified. This output shall contain at least the file system names,
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amount of available space on each of these file systems,
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\ and the number of free file slots, or \fIinodes\fP, available; when
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\fB-t\fP is specified, the output shall contain the
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total allocated space as well.
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.SH OPTIONS
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.LP
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The \fIdf\fP utility shall conform to the Base Definitions volume
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of IEEE\ Std\ 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
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.LP
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The following options shall be supported:
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.TP 7
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\fB-k\fP
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Use 1024-byte units, instead of the default 512-byte units, when writing
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space figures.
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.TP 7
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\fB-P\fP
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Produce output in the format described in the STDOUT section.
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.TP 7
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\fB-t\fP
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Include total allocated-space figures in the output.
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.sp
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.SH OPERANDS
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.LP
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The following operand shall be supported:
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.TP 7
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\fIfile\fP
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A pathname of a file within the hierarchy of the desired file system.
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If a file other than a FIFO, a regular file, a directory,
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\ or a special file representing the device containing the file system
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(for example, \fB/dev/dsk/0s1\fP) is specified, the results are unspecified.
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Otherwise, \fIdf\fP shall write
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the amount of free space in the file system containing the specified
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\fIfile\fP operand.
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.sp
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.SH STDIN
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.LP
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Not used.
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.SH INPUT FILES
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.LP
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None.
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.SH ENVIRONMENT VARIABLES
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.LP
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The following environment variables shall affect the execution of
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\fIdf\fP:
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.TP 7
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\fILANG\fP
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Provide a default value for the internationalization variables that
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are unset or null. (See the Base Definitions volume of
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IEEE\ Std\ 1003.1-2001, Section 8.2, Internationalization Variables
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for
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the precedence of internationalization variables used to determine
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the values of locale categories.)
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.TP 7
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\fILC_ALL\fP
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If set to a non-empty string value, override the values of all the
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other internationalization variables.
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.TP 7
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\fILC_CTYPE\fP
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Determine the locale for the interpretation of sequences of bytes
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of text data as characters (for example, single-byte as
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opposed to multi-byte characters in arguments).
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.TP 7
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\fILC_MESSAGES\fP
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Determine the locale that should be used to affect the format and
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contents of diagnostic messages written to standard error and
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informative messages written to standard output.
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.TP 7
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\fINLSPATH\fP
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Determine the location of message catalogs for the processing of \fILC_MESSAGES
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\&.\fP
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.sp
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.SH ASYNCHRONOUS EVENTS
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.LP
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Default.
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.SH STDOUT
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.LP
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When both the \fB-k\fP and \fB-P\fP options are specified, the following
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header line shall be written (in the POSIX
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locale):
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.sp
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.RS
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.nf
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\fB"Filesystem 1024-blocks Used Available Capacity Mounted on\\n"
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\fP
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.fi
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.RE
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.LP
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When the \fB-P\fP option is specified without the \fB-k\fP option,
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the following header line shall be written (in the POSIX
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locale):
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.sp
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.RS
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.nf
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\fB"Filesystem 512-blocks Used Available Capacity Mounted on\\n"
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\fP
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.fi
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.RE
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.LP
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The implementation may adjust the spacing of the header line and the
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individual data lines so that the information is presented
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in orderly columns.
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.LP
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The remaining output with \fB-P\fP shall consist of one line of information
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for each specified file system. These lines shall
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be formatted as follows:
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.sp
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.RS
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.nf
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\fB"%s %d %d %d %d%% %s\\n", <\fP\fIfile system name\fP\fB>, <\fP\fItotal space\fP\fB>,
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<\fP\fIspace used\fP\fB>, <\fP\fIspace free\fP\fB>, <\fP\fIpercentage used\fP\fB>,
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<\fP\fIfile system root\fP\fB>
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\fP
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.fi
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.RE
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.LP
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In the following list, all quantities expressed in 512-byte units
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(1024-byte when \fB-k\fP is specified) shall be rounded up to
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the next higher unit. The fields are:
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.TP 7
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<\fIfile\ system\ name\fP>
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.sp
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The name of the file system, in an implementation-defined format.
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.TP 7
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<\fItotal\ space\fP>
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The total size of the file system in 512-byte units. The exact meaning
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of this figure is implementation-defined, but should
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include <\fIspace\ used\fP>, <\fIspace\ free\fP>, plus any space reserved
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by the system not normally
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available to a user.
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.TP 7
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<\fIspace\ used\fP>
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The total amount of space allocated to existing files in the file
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system, in 512-byte units.
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.TP 7
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<\fIspace\ free\fP>
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The total amount of space available within the file system for the
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creation of new files by unprivileged users, in 512-byte
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units. When this figure is less than or equal to zero, it shall not
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be possible to create any new files on the file system without
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first deleting others, unless the process has appropriate privileges.
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The figure written may be less than zero.
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.TP 7
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<\fIpercentage\ used\fP>
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.sp
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The percentage of the normally available space that is currently allocated
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to all files on the file system. This shall be
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calculated using the fraction:
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.sp
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.RS
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.nf
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\fB<\fP\fIspace used\fP\fB>/( <\fP\fIspace used\fP\fB>+ <\fP\fIspace free\fP\fB>)
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\fP
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.fi
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.RE
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.LP
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expressed as a percentage. This percentage may be greater than 100
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if <\fIspace\ free\fP> is less than zero. The
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percentage value shall be expressed as a positive integer, with any
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fractional result causing it to be rounded to the next highest
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integer.
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.TP 7
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<\fIfile\ system\ root\fP>
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.sp
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The directory below which the file system hierarchy appears.
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.sp
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.LP
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The output format is unspecified when \fB-t\fP is used.
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.SH STDERR
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.LP
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The standard error shall be used only for diagnostic messages.
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.SH OUTPUT FILES
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.LP
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None.
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.SH EXTENDED DESCRIPTION
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.LP
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None.
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.SH EXIT STATUS
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.LP
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The following exit values shall be returned:
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.TP 7
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\ 0
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Successful completion.
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.TP 7
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>0
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An error occurred.
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.sp
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.SH CONSEQUENCES OF ERRORS
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.LP
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Default.
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.LP
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\fIThe following sections are informative.\fP
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.SH APPLICATION USAGE
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.LP
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On most systems, the "name of the file system, in an implementation-defined
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format" is the special file on which the file
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system is mounted.
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.LP
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On large file systems, the calculation specified for percentage used
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can create huge rounding errors.
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.SH EXAMPLES
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.IP " 1." 4
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The following example writes portable information about the \fB/usr\fP
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file system:
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.sp
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.RS
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.nf
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\fBdf -P /usr
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\fP
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.fi
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.RE
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.LP
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.IP " 2." 4
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Assuming that \fB/usr/src\fP is part of the \fB/usr\fP file system,
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the following produces the same output as the previous
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example:
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.sp
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.RS
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.nf
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\fBdf -P /usr/src
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\fP
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.fi
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.RE
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.LP
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.SH RATIONALE
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.LP
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The behavior of \fIdf\fP with the \fB-P\fP option is the default action
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of the 4.2 BSD \fIdf\fP utility. The uppercase
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\fB-P\fP was selected to avoid collision with a known industry extension
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using \fB-p\fP.
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.LP
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Historical \fIdf\fP implementations vary considerably in their default
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output. It was therefore necessary to describe the
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default output in a loose manner to accommodate all known historical
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implementations and to add a portable option ( \fB-P\fP) to
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provide information in a portable format.
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.LP
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The use of 512-byte units is historical practice and maintains compatibility
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with \fIls\fP
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and other utilities in this volume of IEEE\ Std\ 1003.1-2001. This
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does not mandate that the file system itself be based on
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512-byte blocks. The \fB-k\fP option was added as a compromise measure.
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It was agreed by the standard developers that 512 bytes
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was the best default unit because of its complete historical consistency
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on System V (\fIversus\fP the mixed 512/1024-byte usage
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on BSD systems), and that a \fB-k\fP option to switch to 1024-byte
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units was a good compromise. Users who prefer the more logical
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1024-byte quantity can easily alias \fIdf\fP to \fIdf\fP \fB-k\fP
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without breaking many historical scripts relying on the
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512-byte units.
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.LP
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It was suggested that \fIdf\fP and the various related utilities be
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modified to access a \fIBLOCKSIZE\fP environment variable
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to achieve consistency and user acceptance. Since this is not historical
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practice on any system, it is left as a possible area for
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system extensions and will be re-evaluated in a future version if
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it is widely implemented.
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.SH FUTURE DIRECTIONS
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.LP
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None.
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.SH SEE ALSO
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.LP
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\fIfind\fP
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.SH COPYRIGHT
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Portions of this text are reprinted and reproduced in electronic form
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from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
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-- Portable Operating System Interface (POSIX), The Open Group Base
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Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
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Electrical and Electronics Engineers, Inc and The Open Group. In the
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event of any discrepancy between this version and the original IEEE and
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The Open Group Standard, the original IEEE and The Open Group Standard
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is the referee document. The original Standard can be obtained online at
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http://www.opengroup.org/unix/online.html .
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