and it must work even in a pathological situation where
@samp{42} is a user name that maps to some other user ID, say 1000.
Simply invoking @code{chown 42 F}, will set @file{F}s owner ID to
-1000---not what you intended.
+1000 -- not what you intended.
GNU @command{chown}, @command{chgrp}, @command{chroot}, and @command{id}
provide a way to work around this, that at the same time may result in a
Nearly every command invocation yields an integral @dfn{exit status}
that can be used to change how other commands work.
For the vast majority of commands, an exit status of zero indicates
-success. Failure is indicated by a nonzero value---typically
+success. Failure is indicated by a nonzero value -- typically
@samp{1}, though it may differ on unusual platforms as POSIX
requires only that it be nonzero.
Like @TeX{}, @command{fmt} reads entire ``paragraphs'' before choosing line
breaks; the algorithm is a variant of that given by Donald E. Knuth
and Michael F. Plass in ``Breaking Paragraphs Into Lines'',
-@cite{Software---Practice & Experience} @b{11}, 11 (November 1981),
+@cite{Software: Practice & Experience} @b{11}, 11 (November 1981),
1119--1184.
The program accepts the following options. Also see @ref{Common options}.
With kernel inotify support, output is triggered by file changes
and is generally very prompt.
-Otherwise, @command{tail} sleeps for one second between checks---
-use @option{--sleep-interval=@var{n}} to change that default---which can
+Otherwise, @command{tail} sleeps for one second between checks --
+use @option{--sleep-interval=@var{n}} to change that default -- which can
make the output appear slightly less responsive or bursty.
When using tail without inotify support, you can make it more responsive
by using a sub-second sleep interval, e.g., via an alias like this:
for each given @var{file}, or standard input if none are given or for a
@var{file} of @samp{-}.
-cksum also supports the @option{-a,--algorithm} option to select the
+cksum also supports the @option{-a/--algorithm} option to select the
digest algorithm to use. @command{cksum} is the preferred interface
to these digests, subsuming the other standalone checksumming utilities,
which can be emulated using @code{cksum -a md5 --untagged "$@@"} etc.
@c This example is a bit contrived and needs more explanation.
@c @item
@c Sort records separated by an arbitrary string by using a pipe to convert
-@c each record delimiter string to @samp{\0}, then using sort's -z option,
+@c each record delimiter string to @samp{\0},
+@c then using sort's @option{-z} option,
@c and converting each @samp{\0} back to the original record delimiter.
@c
@c @example
example, the commands @samp{join -o 1.2,2.2} and @samp{join -o '1.2
2.2'} are equivalent.
-All output lines---including those printed because of any -a or -v
-option---are subject to the specified @var{field-list}.
+All output lines -- including those printed because of any @option{-a}
+or @option{-v} option -- are subject to the specified @var{field-list}.
@item -t @var{char}
Use character @var{char} as the input and output field separator.
@opindex -r
@opindex --reverse
@cindex reverse sorting
-Reverse whatever the sorting method is---e.g., list files in reverse
+Reverse whatever the sorting method is -- e.g., list files in reverse
alphabetical order, youngest first, smallest first, or whatever.
This option has no effect when @option{--sort=none} (@option{-U})
is in effect.
@cindex sparse files, copying
@cindex holes, copying files with
@findex read @r{system call, and holes}
-A @dfn{sparse file} contains @dfn{holes}---a sequence of zero bytes that
+A @dfn{sparse file} contains @dfn{holes} -- a sequence of zero bytes that
does not occupy any file system blocks; the @samp{read} system call
reads these as zeros. This can both save considerable space and
increase speed, since many binary files contain lots of consecutive zero
Block sizes (i.e., specified by @var{bytes} strings) must be nonzero.
Any block size you specify via @samp{bs=}, @samp{ibs=}, @samp{obs=}, @samp{cbs=}
-should not be too large---values larger than a few megabytes
+should not be too large -- values larger than a few megabytes
are generally wasteful or (as in the gigabyte..exabyte case) downright
counterproductive or error-inducing.
which can be either an octal number, or a symbolic mode as in
@command{chmod}, with @samp{a=} (no access allowed to anyone) as the
point of departure (@pxref{File permissions}).
-The default mode is @samp{u=rwx,go=rx,a-s}---read, write, and
+The default mode is @samp{u=rwx,go=rx,a-s} -- read, write, and
execute for the owner, read and execute for group and other, and with
set-user-ID and set-group-ID disabled.
This default is not quite the same as @samp{755}, since it disables
types than others, not @emph{everything} can be treated only as the
undifferentiated byte stream of @dfn{normal files}. For example, when a
file is created or removed, the system must record this information,
-which it does in a @dfn{directory}---a special type of file. Although
+which it does in a @dfn{directory} -- a special type of file. Although
you can read directories as normal files, if you're curious, in order
for the system to do its job it must impose a structure, a certain
order, on the bytes of the file. Thus it is a ``special'' type of file.
A @dfn{hard link} is another name for an existing file; the link and the
original are indistinguishable. Technically speaking, they share the
same inode, and the inode contains all the information about a
-file---indeed, it is not incorrect to say that the inode @emph{is} the
+file -- indeed, it is not incorrect to say that the inode @emph{is} the
file. Most systems prohibit making a hard link to
a directory; on those where it is allowed, only the super-user can do
so (and with caution, since creating a cycle will cause problems to many
there are two ways to treat the user's request. @command{ln} can
treat the destination just as it would a normal directory and create
the link in it. On the other hand, the destination can be viewed as a
-non-directory---as the symlink itself. In that case, @command{ln}
+non-directory -- as the symlink itself. In that case, @command{ln}
must delete or backup that symlink before creating the new link.
The default is to treat a destination that is a symlink to a directory
just like a directory.
du --threshold=200MB
@end example
-Here's how you would use @option{--threshold} to find directories and files -
-note the @option{-a} - with an apparent size smaller than or equal to 500 bytes:
+Here's how you would use @option{--threshold} to find directories and
+files -- note the @option{-a} -- with an apparent size smaller than or
+equal to 500 bytes:
@example
du -a -t -500 --apparent-size
@option{--printf} are:
@itemize @bullet
-@item %a - Permission bits in octal (note @samp{#} and @samp{0} printf flags)
-@item %A - Permission bits in symbolic form (similar to @command{ls -ld})
-@item %b - Number of blocks allocated (see @samp{%B})
-@item %B - The size in bytes of each block reported by @samp{%b}
-@item %C - The SELinux security context of a file, if available
-@item %d - Device number in decimal (st_dev)
-@item %D - Device number in hex (st_dev)
-@item %Hd - Major device number in decimal
-@item %Ld - Minor device number in decimal
-@item %f - Raw mode in hex
-@item %F - File type
-@item %g - Group ID of owner
-@item %G - Group name of owner
-@item %h - Number of hard links
-@item %i - Inode number
-@item %m - Mount point (See note below)
-@item %n - File name
-@item %N - Quoted file name with dereference if symbolic link (see below)
-@item %o - Optimal I/O transfer size hint
-@item %s - Total size, in bytes
-@item %r - Device type in decimal (st_rdev)
-@item %R - Device type in hex (st_rdev)
-@item %Hr - Major device type in decimal (see below)
-@item %Lr - Minor device type in decimal (see below)
-@item %t - Major device type in hex (see below)
-@item %T - Minor device type in hex (see below)
-@item %u - User ID of owner
-@item %U - User name of owner
-@item %w - Time of file birth, or @samp{-} if unknown
-@item %W - Time of file birth as seconds since Epoch, or @samp{0}
-@item %x - Time of last access
-@item %X - Time of last access as seconds since Epoch
-@item %y - Time of last data modification
-@item %Y - Time of last data modification as seconds since Epoch
-@item %z - Time of last status change
-@item %Z - Time of last status change as seconds since Epoch
+@item %a -- Permission bits in octal (note @samp{#} and @samp{0} printf flags)
+@item %A -- Permission bits in symbolic form (similar to @command{ls -ld})
+@item %b -- Number of blocks allocated (see @samp{%B})
+@item %B -- The size in bytes of each block reported by @samp{%b}
+@item %C -- The SELinux security context of a file, if available
+@item %d -- Device number in decimal (st_dev)
+@item %D -- Device number in hex (st_dev)
+@item %Hd -- Major device number in decimal
+@item %Ld -- Minor device number in decimal
+@item %f -- Raw mode in hex
+@item %F -- File type
+@item %g -- Group ID of owner
+@item %G -- Group name of owner
+@item %h -- Number of hard links
+@item %i -- Inode number
+@item %m -- Mount point (See note below)
+@item %n -- File name
+@item %N -- Quoted file name with dereference if symbolic link (see below)
+@item %o -- Optimal I/O transfer size hint
+@item %s -- Total size, in bytes
+@item %r -- Device type in decimal (st_rdev)
+@item %R -- Device type in hex (st_rdev)
+@item %Hr -- Major device type in decimal (see below)
+@item %Lr -- Minor device type in decimal (see below)
+@item %t -- Major device type in hex (see below)
+@item %T -- Minor device type in hex (see below)
+@item %u -- User ID of owner
+@item %U -- User name of owner
+@item %w -- Time of file birth, or @samp{-} if unknown
+@item %W -- Time of file birth as seconds since Epoch, or @samp{0}
+@item %x -- Time of last access
+@item %X -- Time of last access as seconds since Epoch
+@item %y -- Time of last data modification
+@item %Y -- Time of last data modification as seconds since Epoch
+@item %z -- Time of last status change
+@item %Z -- Time of last status change as seconds since Epoch
@end itemize
The @samp{%a} format prints the octal mode, and so it is useful
you must use a different set of @var{format} directives:
@itemize @bullet
-@item %a - Free blocks available to non-super-user
-@item %b - Total data blocks in file system
-@item %c - Total file nodes in file system
-@item %d - Free file nodes in file system
-@item %f - Free blocks in file system
-@item %i - File System ID in hex
-@item %l - Maximum length of file names
-@item %n - File name
-@item %s - Block size (for faster transfers)
-@item %S - Fundamental block size (for block counts)
-@item %t - Type in hex
-@item %T - Type in human readable form
+@item %a -- Free blocks available to non-super-user
+@item %b -- Total data blocks in file system
+@item %c -- Total file nodes in file system
+@item %d -- Free file nodes in file system
+@item %f -- Free blocks in file system
+@item %i -- File System ID in hex
+@item %l -- Maximum length of file names
+@item %n -- File name
+@item %s -- Block size (for faster transfers)
+@item %S -- Fundamental block size (for block counts)
+@item %t -- Type in hex
+@item %T -- Type in human readable form
@end itemize
@vindex TZ
@cindex redirection
@cindex commands for redirection
-Unix shells commonly provide several forms of @dfn{redirection}---ways
+Unix shells commonly provide several forms of @dfn{redirection} -- ways
to change the input source or output destination of a command. But one
useful redirection is performed by a separate command, not by the shell;
it's described here.
file being written to already exists, the data it previously contained
is overwritten unless the @option{-a} option is used.
-In previous versions of GNU Coreutils (v5.3.0 -- v8.23),
+In previous versions of GNU Coreutils (5.3.0--8.23),
a @var{file} of @samp{-}
caused @command{tee} to send another copy of input to standard output.
However, as the interleaved output was not very useful, @command{tee} now
@opindex -P
@opindex --physical
Print a fully resolved name for the current directory. That is, all
-components of the printed name will be actual directory names---none
+components of the printed name will be actual directory names -- none
will be symbolic links.
@end table
Here the first trap command sets SIGPIPE to ignore.
The second trap command ostensibly sets it back to its default,
but POSIX mandates that the shell must not change inherited
-state of the signal - so it is a no-op.
+state of the signal -- so it is a no-op.
@example
trap '' PIPE && sh -c 'trap - PIPE ; seq inf | head -n1'
Ignore signal @var{sig} when running a program. Without @var{sig} all
known signals are set to ignore. Multiple signals can be comma-separated.
An empty @var{sig} argument is a no-op. The following command runs @command{seq}
-with SIGINT set to be ignored - pressing @kbd{Ctrl-C} will not terminate it:
+with SIGINT set to be ignored -- pressing @kbd{Ctrl-C} will not terminate it:
@example
env --ignore-signal=INT seq inf > /dev/null
The @option{iec} option uses a single letter suffix (e.g. @samp{G}), which is
not fully standard, as the @emph{iec} standard recommends a two-letter symbol
-(e.g @samp{Gi}) - but in practice, this method common. Compare with
+(e.g @samp{Gi}) -- but in practice, this method is common. Compare with
the @option{iec-i} option.
@item iec-i
On the other hand, an experienced carpenter doesn't build a house using
a Swiss Army knife. Instead, he has a toolbox chock full of specialized
-tools---a saw, a hammer, a screwdriver, a plane, and so on. And he knows
+tools -- a saw, a hammer, a screwdriver, a plane, and so on. And he knows
exactly when and where to use each tool; you won't catch him hammering nails
with the handle of his screwdriver.
Instead, they felt that programs should be specialized tools. In short, each
program ``should do one thing well.'' No more and no less. Such programs are
-simpler to design, write, and get right---they only do one thing.
+simpler to design, write, and get right -- they only do one thing.
Furthermore, they found that with the right machinery for hooking programs
together, that the whole was greater than the sum of the parts. By combining
projects / thirdparty / coreutils.git / commitdiff
