coreutils.texi

Linux下文件工具。

@item --traditional
@opindex --traditional
Recognize the non-option arguments that traditional @command{od}
accepted.  The following syntax:

@smallexample
od --traditional [@var{file}] [[+]@var{offset}[.][b] [[+]@var{label}[.][b]]]
@end smallexample

@noindent
can be used to specify at most one file and optional arguments
specifying an offset and a pseudo-start address, @var{label}.  By
default, @var{offset} is interpreted as an octal number specifying how
many input bytes to skip before formatting and writing.  The optional
trailing decimal point forces the interpretation of @var{offset} as a
decimal number.  If no decimal is specified and the offset begins with
@samp{0x} or @samp{0X} it is interpreted as a hexadecimal number.  If
there is a trailing @samp{b}, the number of bytes skipped will be
@var{offset} multiplied by 512.  The @var{label} argument is interpreted
just like @var{offset}, but it specifies an initial pseudo-address.  The
pseudo-addresses are displayed in parentheses following any normal
address.

@end table


@node Formatting file contents
@chapter Formatting file contents

@cindex formatting file contents

These commands reformat the contents of files.

@menu
* fmt invocation::              Reformat paragraph text.
* pr invocation::               Paginate or columnate files for printing.
* fold invocation::             Wrap input lines to fit in specified width.
@end menu


@node fmt invocation
@section @command{fmt}: Reformat paragraph text

@pindex fmt
@cindex reformatting paragraph text
@cindex paragraphs, reformatting
@cindex text, reformatting

@command{fmt} fills and joins lines to produce output lines of (at most)
a given number of characters (75 by default).  Synopsis:

@example
fmt [@var{option}]@dots{} [@var{file}]@dots{}
@end example

@command{fmt} reads from the specified @var{file} arguments (or standard
input if none are given), and writes to standard output.

By default, blank lines, spaces between words, and indentation are
preserved in the output; successive input lines with different
indentation are not joined; tabs are expanded on input and introduced on
output.

@cindex line-breaking
@cindex sentences and line-breaking
@cindex Knuth, Donald E.
@cindex Plass, Michael F.
@command{fmt} prefers breaking lines at the end of a sentence, and tries to
avoid line breaks after the first word of a sentence or before the last
word of a sentence.  A @dfn{sentence break} is defined as either the end
of a paragraph or a word ending in any of @samp{.?!}, followed by two
spaces or end of line, ignoring any intervening parentheses or quotes.
Like @TeX{}, @command{fmt} reads entire ``paragraphs'' before choosing line
breaks; the algorithm is a variant of that in ``Breaking Paragraphs Into
Lines'' (Donald E. Knuth and Michael F. Plass, @cite{Software---Practice
and Experience}, 11 (1981), 1119--1184).

The program accepts the following options.  Also see @ref{Common options}.

@table @samp

@item -c
@itemx --crown-margin
@opindex -c
@opindex --crown-margin
@cindex crown margin
@dfn{Crown margin} mode: preserve the indentation of the first two
lines within a paragraph, and align the left margin of each subsequent
line with that of the second line.

@item -t
@itemx --tagged-paragraph
@opindex -t
@opindex --tagged-paragraph
@cindex tagged paragraphs
@dfn{Tagged paragraph} mode: like crown margin mode, except that if
indentation of the first line of a paragraph is the same as the
indentation of the second, the first line is treated as a one-line
paragraph.

@item -s
@itemx --split-only
@opindex -s
@opindex --split-only
Split lines only.  Do not join short lines to form longer ones.  This
prevents sample lines of code, and other such ``formatted'' text from
being unduly combined.

@item -u
@itemx --uniform-spacing
@opindex -u
@opindex --uniform-spacing
Uniform spacing.  Reduce spacing between words to one space, and spacing
between sentences to two spaces.

@item -@var{width}
@itemx -w @var{width}
@itemx --width=@var{width}
@opindex -@var{width}
@opindex -w
@opindex --width
Fill output lines up to @var{width} characters (default 75).  @command{fmt}
initially tries to make lines about 7% shorter than this, to give it
room to balance line lengths.

@item -p @var{prefix}
@itemx --prefix=@var{prefix}
Only lines beginning with @var{prefix} (possibly preceded by whitespace)
are subject to formatting. The prefix and any preceding whitespace are
stripped for the formatting and then re-attached to each formatted output
line.  One use is to format certain kinds of program comments, while
leaving the code unchanged.

@end table


@node pr invocation
@section @command{pr}: Paginate or columnate files for printing

@pindex pr
@cindex printing, preparing files for
@cindex multicolumn output, generating
@cindex merging files in parallel

@command{pr} writes each @var{file} (@samp{-} means standard input), or
standard input if none are given, to standard output, paginating and
optionally outputting in multicolumn format; optionally merges all
@var{file}s, printing all in parallel, one per column.  Synopsis:

@example
pr [@var{option}]@dots{} [@var{file}]@dots{}
@end example

@vindex LC_MESSAGES
By default, a 5-line header is printed at each page: two blank lines;
a line with the date, the filename, and the page count; and two more
blank lines.  A footer of five blank lines is also printed.
With the @option{-F}
option, a 3-line header is printed: the leading two blank lines are
omitted; no footer is used.  The default @var{page_length} in both cases is 66
lines.  The default number of text lines changes from 56 (without @option{-F})
to 63 (with @option{-F}).  The text line of the header takes the form
@samp{@var{date} @var{string} @var{page}}, with spaces inserted around
@var{string} so that the line takes up the full @var{page_width}.  Here,
@var{date} is the date (see the @option{-D} or @option{--date-format}
option for details), @var{string} is the centered header string, and
@var{page} identifies the page number.  The @env{LC_MESSAGES} locale
category affects the spelling of @var{page}; in the default C locale, it
is @samp{Page @var{number}} where @var{number} is the decimal page
number.

Form feeds in the input cause page breaks in the output.  Multiple form
feeds produce empty pages.

Columns are of equal width, separated by an optional string (default
is @samp{space}).  For multicolumn output, lines will always be truncated to
@var{page_width} (default 72), unless you use the @option{-J} option.
For single
column output no line truncation occurs by default.  Use @option{-W} option to
truncate lines in that case.

The following changes were made in version 1.22i and apply to later
versions of @command{pr}:
@c FIXME: this whole section here sounds very awkward to me. I
@c made a few small changes, but really it all needs to be redone. - Brian
@c OK, I fixed another sentence or two, but some of it I just don't understand.
@ - Brian
@itemize @bullet

@item
Some small @var{letter options} (@option{-s}, @option{-w}) have been
redefined for better @acronym{POSIX} compliance.  The output of some further
cases has been adapted to other Unix systems.  These changes are not
compatible with earlier versions of the program.

@item
Some @var{new capital letter} options (@option{-J}, @option{-S}, @option{-W})
have been introduced to turn off unexpected interferences of small letter
options.  The @option{-N} option and the second argument @var{last_page}
of @samp{+FIRST_PAGE} offer more flexibility.  The detailed handling of
form feeds set in the input files requires the @option{-T} option.

@item
Capital letter options override small letter ones.

@item
Some of the option-arguments (compare @option{-s}, @option{-e},
@option{-i}, @option{-n}) cannot be specified as separate arguments from the
preceding option letter (already stated in the @acronym{POSIX} specification).
@end itemize

The program accepts the following options.  Also see @ref{Common options}.

@table @samp

@item +@var{first_page}[:@var{last_page}]
@itemx --pages=@var{first_page}[:@var{last_page}]
@c The two following @opindex lines evoke warnings because they contain `:'
@c The `info' spec does not permit that.  If we use those lines, we end
@c up with truncated index entries that don't work.
@c @opindex +@var{first_page}[:@var{last_page}]
@c @opindex --pages=@var{first_page}[:@var{last_page}]
@opindex +@var{page_range}
@opindex --pages=@var{page_range}
Begin printing with page @var{first_page} and stop with @var{last_page}.
Missing @samp{:@var{last_page}} implies end of file.  While estimating
the number of skipped pages each form feed in the input file results
in a new page.  Page counting with and without @samp{+@var{first_page}}
is identical.  By default, counting starts with the first page of input
file (not first page printed).  Line numbering may be altered by @option{-N}
option.

@item -@var{column}
@itemx --columns=@var{column}
@opindex -@var{column}
@opindex --columns
@cindex down columns
With each single @var{file}, produce @var{column} columns of output
(default is 1) and print columns down, unless @option{-a} is used.  The
column width is automatically decreased as @var{column} increases; unless
you use the @option{-W/-w} option to increase @var{page_width} as well.
This option might well cause some lines to be truncated.  The number of
lines in the columns on each page are balanced.  The options @option{-e}
and @option{-i} are on for multiple text-column output.  Together with
@option{-J} option column alignment and line truncation is turned off.
Lines of full length are joined in a free field format and @option{-S}
option may set field separators.  @option{-@var{column}} may not be used
with @option{-m} option.

@item -a
@itemx --across
@opindex -a
@opindex --across
@cindex across columns
With each single @var{file}, print columns across rather than down.  The
@option{-@var{column}} option must be given with @var{column} greater than one.
If a line is too long to fit in a column, it is truncated.

@item -c
@itemx --show-control-chars
@opindex -c
@opindex --show-control-chars
Print control characters using hat notation (e.g., @samp{^G}); print
other nonprinting characters in octal backslash notation.  By default,
nonprinting characters are not changed.

@item -d
@itemx --double-space
@opindex -d
@opindex --double-space
@cindex double spacing
Double space the output.

@item -D @var{format}
@itemx --date-format=@var{format}
@cindex time formats
@cindex formatting times
Format header dates using @var{format}, using the same conventions as
for the the command @samp{date +@var{format}}; @xref{date invocation}.
Except for directives, which start with
@samp{%}, characters in @var{format} are printed unchanged.  You can use
this option to specify an arbitrary string in place of the header date,
e.g., @option{--date-format="Monday morning"}.

@vindex POSIXLY_CORRECT
@vindex LC_TIME
If the @env{POSIXLY_CORRECT} environment variable is not set, the date
format defaults to @samp{%Y-%m-%d %H:%M} (for example, @samp{2001-12-04
23:59}); otherwise, the format depends on the @env{LC_TIME} locale
category, with the default being @samp{%b %e %H:%M %Y} (for example,
@samp{Dec@ @ 4 23:59 2001}.

@item -e[@var{in-tabchar}[@var{in-tabwidth}]]
@itemx --expand-tabs[=@var{in-tabchar}[@var{in-tabwidth}]]
@opindex -e
@opindex --expand-tabs
@cindex input tabs
Expand @var{tab}s to spaces on input.  Optional argument @var{in-tabchar} is
the input tab character (default is the TAB character).  Second optional
argument @var{in-tabwidth} is the input tab character's width (default
is 8).

@item -f
@itemx -F
@itemx --form-feed
@opindex -F
@opindex -f
@opindex --form-feed
Use a form feed instead of newlines to separate output pages.  The default
page length of 66 lines is not altered.  But the number of lines of text
per page changes from default 56 to 63 lines.

@item -h @var{HEADER}
@itemx --header=@var{HEADER}
@opindex -h
@opindex --header
Replace the filename in the header with the centered string @var{header}.
When using the shell, @var{header} should be quoted and should be
separated from @option{-h} by a space.

@item -i[@var{out-tabchar}[@var{out-tabwidth}]]
@itemx --output-tabs[=@var{out-tabchar}[@var{out-tabwidth}]]
@opindex -i
@opindex --output-tabs
@cindex output tabs
Replace spaces with @var{tab}s on output.  Optional argument @var{out-tabchar}
is the output tab character (default is the TAB character).  Second optional
argument @var{out-tabwidth} is the output tab character's width (default
is 8).

@item -J
@itemx --join-lines
@opindex -J
@opindex --join-lines
Merge lines of full length.  Used together with the column options
@option{-@var{column}}, @option{-a -@var{column}} or @option{-m}.  Turns off
@option{-W/-w} line truncation;
no column alignment used; may be used with
@option{--sep-string[=@var{string}]}.  @option{-J} has been introduced
(together with @option{-W} and @option{--sep-string})
to disentangle the old (@acronym{POSIX}-compliant) options @option{-w} and
@option{-s} along with the three column options.


@item -l @var{page_length}
@itemx --length=@var{page_length}
@opindex -l
@opindex --length
Set the page length to @var{page_length} (default 66) lines, including
the lines of the header [and the footer].  If @var{page_length} is less
than or equal to 10 (or <= 3 with @option{-F}), the header and footer are
omitted, and all form feeds set in input files are eliminated, as if
the @option{-T} option had been given.

@item -m
@itemx --merge
@opindex -m
@opindex --merge
Merge and print all @va