coreutils.texi

Linux下文件工具。

@command{stty}: Print or change terminal characteristics

* Control::                     Control settings
* Input::                       Input settings
* Output::                      Output settings
* Local::                       Local settings
* Combination::                 Combination settings
* Characters::                  Special characters
* Special::                     Special settings

User information

* id invocation::                Print real and effective uid and gid
* logname invocation::           Print current login name
* whoami invocation::            Print effective user id
* groups invocation::            Print group names a user is in
* users invocation::             Print login names of users currently logged in
* who invocation::               Print who is currently logged in

System context

* date invocation::              Print or set system date and time
* uname invocation::             Print system information
* hostname invocation::          Print or set system name
* hostid invocation::            Print numeric host identifier.

@command{date}: Print or set system date and time

* Time directives::              Time directives
* Date directives::              Date directives
* Literal directives::           Literal directives
* Padding::                      Padding
* Setting the time::             Setting the time
* Options for date::             Options for @command{date}
* Examples of date::             Examples of @command{date}

Modified command invocation

* chroot invocation::            Run a command with a different root directory
* env invocation::               Run a command in a modified environment
* nice invocation::              Run a command with modified scheduling priority
* nohup invocation::             Run a command immune to hangups
* su invocation::                Run a command with substitute user and group id

Process control

* kill invocation::              Sending a signal to processes.

Delaying

* sleep invocation::             Delay for a specified time

Numeric operations

* factor invocation::            Print prime factors
* seq invocation::               Print numeric sequences

File permissions

* Mode Structure::               Structure of File Permissions
* Symbolic Modes::               Mnemonic permissions representation
* Numeric Modes::                Permissions as octal numbers

Date input formats

* General date syntax:           General date syntax
* Calendar date items:           Calendar date items
* Time of day items:             Time of day items
* Time zone items:               Time zone items
* Day of week items:             Day of week items
* Relative items in date strings:  Relative items in date strings
* Pure numbers in date strings:  Pure numbers in date strings
* Authors of getdate:            Authors of getdate

Opening the software toolbox

* Toolbox introduction::         Toolbox introduction
* I/O redirection::              I/O redirection
* The who command::              The @command{who} command
* The cut command::              The @command{cut} command
* The sort command::             The @command{sort} command
* The uniq command::             The @command{uniq} command
* Putting the tools together::   Putting the tools together

GNU Free Documentation License

* How to use this License for your documents::

@end detailmenu
@end menu


@node Introduction
@chapter Introduction

This manual is a work in progress: many sections make no attempt to explain
basic concepts in a way suitable for novices.  Thus, if you are interested,
please get involved in improving this manual.  The entire @sc{gnu} community
will benefit.

@cindex @acronym{POSIX}
The @sc{gnu} utilities documented here are mostly compatible with the
@acronym{POSIX} standard.
@cindex bugs, reporting
Please report bugs to @email{bug-coreutils@@gnu.org}.  Remember
to include the version number, machine architecture, input files, and
any other information needed to reproduce the bug: your input, what you
expected, what you got, and why it is wrong.  Diffs are welcome, but
please include a description of the problem as well, since this is
sometimes difficult to infer. @xref{Bugs, , , gcc, Using and Porting GNU CC}.

@cindex Berry, K.
@cindex Paterson, R.
@cindex Stallman, R.
@cindex Pinard, F.
@cindex MacKenzie, D.
@cindex Meyering, J.
@cindex Youmans, B.
This manual was originally derived from the Unix man pages in the
distributions, which were written by David MacKenzie and updated by Jim
Meyering.  What you are reading now is the authoritative documentation
for these utilities; the man pages are no longer being maintained.  The
original @command{fmt} man page was written by Ross Paterson.  Fran@,{c}ois
Pinard did the initial conversion to Texinfo format.  Karl Berry did the
indexing, some reorganization, and editing of the results.  Brian
Youmans of the Free Software Foundation office staff combined the
manuals for textutils, fileutils, and sh-utils to produce the present
omnibus manual.  Richard Stallman contributed his usual invaluable
insights to the overall process.

@node Common options
@chapter Common options

@cindex common options

Certain options are available in all of these programs.  Rather than
writing identical descriptions for each of the programs, they are
described here.  (In fact, every @sc{gnu} program accepts (or should accept)
these options.)

@vindex POSIXLY_CORRECT
Normally options and operands can appear in any order, and programs act
as if all the options appear before any operands.  For example,
@samp{sort -r passwd -t :} acts like @samp{sort -r -t : passwd}, since
@samp{:} is an option-argument of @option{-t}.  However, if the
@env{POSIXLY_CORRECT} environment variable is set, options must appear
before operands, unless otherwise specified for a particular command.

Some of these programs recognize the @option{--help} and @option{--version}
options only when one of them is the sole command line argument.

@table @samp

@item --help
@opindex --help
@cindex help, online
Print a usage message listing all available options, then exit successfully.

@item --version
@opindex --version
@cindex version number, finding
Print the version number, then exit successfully.

@item --
@opindex --
@cindex option delimiter
Delimit the option list.  Later arguments, if any, are treated as
operands even if they begin with @samp{-}.  For example, @samp{sort --
-r} reads from the file named @file{-r}.

@end table

@cindex standard input
@cindex standard output
A single @samp{-} is not really an option, though it looks like one.  It
stands for standard input, or for standard output if that is clear from
the context, and it can be used either as an operand or as an
option-argument.  For example, @samp{sort -o - -} outputs to standard
output and reads from standard input, and is equivalent to plain
@samp{sort}.  Unless otherwise specified, @samp{-} can appear in any
context that requires a file name.

@menu
* Backup options::              -b -S -V, in some programs.
* Block size::                  BLOCK_SIZE and --block-size, in some programs.
* Target directory::            --target-directory, in some programs.
* Trailing slashes::            --strip-trailing-slashes, in some programs.
* Standards conformance::       Conformance to the @acronym{POSIX} standard.
@end menu


@node Backup options
@section Backup options

@cindex backup options

Some @sc{gnu} programs (at least @command{cp}, @code{install}, @code{ln}, and
@command{mv}) optionally make backups of files before writing new versions.
These options control the details of these backups.  The options are also
briefly mentioned in the descriptions of the particular programs.

@table @samp

@item -b
@itemx @w{@kbd{--backup}[=@var{method}]}
@opindex -b
@opindex --backup
@vindex VERSION_CONTROL
@cindex backups, making
Make a backup of each file that would otherwise be overwritten or removed.
Without this option, the original versions are destroyed.
Use @var{method} to determine the type of backups to make.
When this option is used but @var{method} is not specified,
then the value of the @env{VERSION_CONTROL}
environment variable is used.  And if @env{VERSION_CONTROL} is not set,
the default backup type is @samp{existing}.

Note that the short form of this option, @option{-b} does not accept any
argument.  Using @option{-b} is equivalent to using @option{--backup=existing}.

@vindex version-control @r{Emacs variable}
This option corresponds to the Emacs variable @samp{version-control};
the values for @var{method} are the same as those used in Emacs.
This option also accepts more descriptive names.
The valid @var{method}s are (unique abbreviations are accepted):

@table @samp
@item none
@itemx off
@opindex none @r{backup method}
Never make backups.

@item numbered
@itemx t
@opindex numbered @r{backup method}
Always make numbered backups.

@item existing
@itemx nil
@opindex existing @r{backup method}
Make numbered backups of files that already have them, simple backups
of the others.

@item simple
@itemx never
@opindex simple @r{backup method}
Always make simple backups.  Please note @samp{never} is not to be
confused with @samp{none}.

@end table

@item -S @var{suffix}
@itemx --suffix=@var{suffix}
@opindex -S
@opindex --suffix
@cindex backup suffix
@vindex SIMPLE_BACKUP_SUFFIX
Append @var{suffix} to each backup file made with @option{-b}.  If this
option is not specified, the value of the @env{SIMPLE_BACKUP_SUFFIX}
environment variable is used.  And if @env{SIMPLE_BACKUP_SUFFIX} is not
set, the default is @samp{~}, just as in Emacs.

@itemx --version-control=@var{method}
@opindex --version-control
@c FIXME: remove this block one or two releases after the actual
@c removal from the code.
This option is obsolete and will be removed in a future release.
It has been replaced with @w{@kbd{--backup}}.

@end table

@node Block size
@section Block size

@cindex block size

Some @sc{gnu} programs (at least @command{df}, @code{du}, and @code{ls}) display
file sizes in ``blocks''.  You can adjust the block size to make file
sizes easier to read.  The block size used for display is independent of
any filesystem block size.

Normally, disk usage sizes are rounded up, disk free space sizes are
rounded down, and other sizes are rounded to the nearest value with ties
rounding to an even value.

@opindex --block-size=@var{size}
@vindex BLOCK_SIZE
@vindex DF_BLOCK_SIZE
@vindex DU_BLOCK_SIZE
@vindex LS_BLOCK_SIZE
@vindex POSIXLY_CORRECT@r{, and block size}

The default block size is chosen by examining the following environment
variables in turn; the first one that is set determines the block size.

@table @code

@item DF_BLOCK_SIZE
This specifies the default block size for the @command{df} command.
Similarly, @env{DU_BLOCK_SIZE} specifies the default for @command{du} and
@env{LS_BLOCK_SIZE} for @command{ls}.

@item BLOCK_SIZE
This specifies the default block size for all three commands, if the
above command-specific environment variables are not set.

@item POSIXLY_CORRECT
If neither the @env{@var{command}_BLOCK_SIZE} nor the @env{BLOCK_SIZE}
variables are set, but this variable is set, the block size defaults to 512.

@end table

If none of the above environment variables are set, the block size
currently defaults to 1024 bytes, but this number may change in the
future.

@cindex human-readable output
@cindex SI output

A block size specification can be a positive integer specifying the number
of bytes per block, or it can be @code{human-readable} or @code{si} to
select a human-readable format.  Integers may be followed by suffixes
that are upward compatible with the
@uref{http://www.bipm.fr/enus/3_SI/si-prefixes.html, SI prefixes}
for decimal multiples and with the
@uref{http://physics.nist.gov/cuu/Units/binary.html, IEC 60027-2
prefixes for binary multiples}.

With human-readable formats, output sizes are followed by a size letter
such as @samp{M} for megabytes.  @code{BLOCK_SIZE=human-readable} uses
powers of 1024; @samp{M} stands for 1,048,576 bytes.
@code{BLOCK_SIZE=si} is similar, but uses powers of 1000 and appends
@samp{B}; @samp{MB} stands for 1,000,000 bytes.

An integer block size can be followed by a suffix to specify a
multiple of that size; in this case an omitted integer is understood
to be 1.  A bare size letter, or one followed by @samp{iB}, specifies
a multiple using powers of 1024.  A size letter followed by @samp{B}
specifies powers of 1000 instead.  For example, @samp{M} and
@samp{MiB} are equivalent to @samp{1048576}, whereas @samp{MB} is
equivalent to @samp{1000000}.

The following suffixes are defined.  Large sizes like @code{1Y}
may be rejected by your computer due to limitations of its arithmetic.

@table @samp
@item kB
@cindex kilobyte, definition of
kilobyte: @math{10^3 = 1000}.
@item k
@itemx K
@itemx KiB
@cindex kibibyte, definition of
kibibyte: @math{2^10 = 1024}.  @samp{K} is special: the SI prefix is
@samp{k} and the IEC 60027-2 prefix is @samp{Ki}, but tradition and
@acronym{POSIX} use @samp{k} to mean @samp{KiB}.
@item MB
@cindex megabyte, definition of
megabyte: @math{10^6 = 1,000,000}.
@item M
@itemx MiB