man/cat1p/df.1p.txt
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df(P) df(P)
NAME df - report free disk space SYNOPSIS df [-k][-P|-t][file...]<img src="../images/opt-end.gif" alt="[Option End]" border="0"> DESCRIPTION The df utility shall write the amount of available space <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> and file slots for file systems on which the invoking user has appropriate read access. File sys- tems shall be specified by the file operands; when none are specified, information shall be written for all file systems. The format of the default output from df is unspecified, but all space figures are reported in 512-byte units, unless the -k option is specified. This output shall contain at least the file system names, amount of available space on each of these file systems, and the number of free file slots, or inodes, avail- able; when -t is specified, the output shall contain the total allocated space as well. OPTIONS The df utility shall conform to the Base Definitions volume of IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines. The following options shall be supported: -k Use 1024-byte units, instead of the default 512-byte units, when writing space figures. -P Produce output in the format described in the STDOUT section. -t Include total allocated-space figures in the out- put. OPERANDS The following operand shall be supported: file A pathname of a file within the hierarchy of the desired file system. If a file other than a FIFO, a regular file, a directory, or a special file representing the device containing the file system (for example, /dev/dsk/0s1) is specified, the results are unspecified. Otherwise, df shall write the amount of free space in the file system containing the specified file operand. STDIN Not used. INPUT FILES None. ENVIRONMENT VARIABLES The following environment variables shall affect the execution of df: LANG Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of IEEE Std 1003.1-2001, Section 8.2, International- ization Variables for the precedence of interna- tionalization variables used to determine the values of locale categories.) LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_CTYPE Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to multi- byte characters in arguments). LC_MESSAGES Determine the locale that should be used to affect the format and contents of diagnostic mes- sages written to standard error and informative messages written to standard output. NLSPATH Determine the location of message catalogs for the processing of LC_MESSAGES . ASYNCHRONOUS EVENTS Default. STDOUT When both the -k and -P options are specified, the fol- lowing header line shall be written (in the POSIX locale): "Filesystem 1024-blocks Used Available Capacity Mounted on\n" When the -P option is specified without the -k option, the following header line shall be written (in the POSIX locale): "Filesystem 512-blocks Used Available Capacity Mounted on\n" The implementation may adjust the spacing of the header line and the individual data lines so that the informa- tion is presented in orderly columns. The remaining output with -P shall consist of one line of information for each specified file system. These lines shall be formatted as follows: "%s %d %d %d %d%% %s\n", <file system name>, <total space>, <space used>, <space free>, <percentage used>, <file system root> In the following list, all quantities expressed in 512-byte units (1024-byte when -k is specified) shall be rounded up to the next higher unit. The fields are: <file system name> The name of the file system, in an implementa- tion-defined format. <total space> The total size of the file system in 512-byte units. The exact meaning of this figure is imple- mentation-defined, but should include <space used>, <space free>, plus any space reserved by the system not normally available to a user. <space used> The total amount of space allocated to existing files in the file system, in 512-byte units. <space free> The total amount of space available within the file system for the creation of new files by unprivileged users, in 512-byte units. When this figure is less than or equal to zero, it shall not be possible to create any new files on the file system without first deleting others, unless the process has appropriate privileges. The fig- ure written may be less than zero. <percentage used> The percentage of the normally available space that is currently allocated to all files on the file system. This shall be calculated using the fraction: <space used>/( <space used>+ <space free>) expressed as a percentage. This percentage may be greater than 100 if <space free> is less than zero. The percentage value shall be expressed as a positive inte- ger, with any fractional result causing it to be rounded to the next highest integer. <file system root> The directory below which the file system hierar- chy appears. The output format is unspecified when -t is used. STDERR The standard error shall be used only for diagnostic messages. OUTPUT FILES None. EXTENDED DESCRIPTION None. EXIT STATUS The following exit values shall be returned: 0 Successful completion. >0 An error occurred. CONSEQUENCES OF ERRORS Default. The following sections are informative. APPLICATION USAGE On most systems, the "name of the file system, in an implementation-defined format" is the special file on which the file system is mounted. On large file systems, the calculation specified for percentage used can create huge rounding errors. EXAMPLES The following example writes portable information about the /usr file system: df -P /usr Assuming that /usr/src is part of the /usr file system, the following produces the same output as the previous example: df -P /usr/src RATIONALE The behavior of df with the -P option is the default action of the 4.2 BSD df utility. The uppercase -P was selected to avoid collision with a known industry exten- sion using -p. Historical df implementations vary considerably in their default output. It was therefore necessary to describe the default output in a loose manner to accommodate all known historical implementations and to add a portable option ( -P) to provide information in a portable for- mat. The use of 512-byte units is historical practice and maintains compatibility with ls and other utilities in this volume of IEEE Std 1003.1-2001. This does not man- date that the file system itself be based on 512-byte blocks. The -k option was added as a compromise measure. It was agreed by the standard developers that 512 bytes was the best default unit because of its complete his- torical consistency on System V (versus the mixed 512/1024-byte usage on BSD systems), and that a -k option to switch to 1024-byte units was a good compro- mise. Users who prefer the more logical 1024-byte quan- tity can easily alias df to df -k without breaking many historical scripts relying on the 512-byte units. It was suggested that df and the various related utili- ties be modified to access a BLOCKSIZE environment vari- able to achieve consistency and user acceptance. Since this is not historical practice on any system, it is left as a possible area for system extensions and will be re-evaluated in a future version if it is widely implemented. FUTURE DIRECTIONS None. SEE ALSO find COPYRIGHT Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operat- ing System Interface (POSIX), The Open Group Base Speci- fications Issue 6, Copyright (C) 2001-2003 by the Insti- tute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.open- group.org/unix/online.html . POSIX 2003 df(P) |