sort.html

unix 下的C开发手册,还用详细的例程。

<dt><i>NLSPATH</i><dd>
Determine the location of message catalogues
for the processing of
<i>LC_MESSAGES .
</i>
</dl>
</blockquote><h4><a name = "tag_001_014_2038">&nbsp;</a>ASYNCHRONOUS EVENTS</h4><blockquote>
Default.
</blockquote><h4><a name = "tag_001_014_2039">&nbsp;</a>STDOUT</h4><blockquote>
Unless the
<b>-o</b>
or
<b>-c</b>
options are in effect, the standard output contains the sorted input.
</blockquote><h4><a name = "tag_001_014_2040">&nbsp;</a>STDERR</h4><blockquote>
Used for diagnostic messages.
A warning message about correcting an incomplete last line
of an input file may be generated, but need not affect the
final exit status.
</blockquote><h4><a name = "tag_001_014_2041">&nbsp;</a>OUTPUT FILES</h4><blockquote>
If the
<b>-o</b>
option is in effect, the sorted input is placed in the file
<i>output</i>.
</blockquote><h4><a name = "tag_001_014_2042">&nbsp;</a>EXTENDED DESCRIPTION</h4><blockquote>
The notation:
<pre>
<code>
-k&nbsp;<i>field_start</i><b>[</b><i>type</i><b>][</b>,<i>field_end</i><b>[</b><i>type</i><b>]]
</b></code>
</pre>
defines a key field that begins at
<i>field_start</i>
and ends at
<i>field_end</i>
inclusive, unless
<i>field_start</i>
falls beyond the end of the line or after
<i>field_end</i>,
in which case the key field is empty.
A missing
<i>field_end</i>
means the last character of the line.
<p>
A field comprises a maximal sequence
of non-separating characters and,
in the absence of option
<b>-t</b>,
any preceding field separator.
<p>
The
<i>field_start</i>
portion of the
<i>keydef</i>
option-argument has the form:
<pre>
<code>
<i>field_number</i><b>[</b>.<i>first_character</i><b>]
</b></code>
</pre>
<p>
Fields and characters within fields are numbered starting with 1.
The
<i>field_number</i>
and
<i>first_character</i>
pieces, interpreted as positive
decimal integers, specify the first character to be used as part of
a sort key.
If
<i>.first_character</i>
is omitted, it refers to the first character of the field.
<p>
The
<i>field_end</i>
portion of the
<i>keydef</i>
option-argument has the form:
<pre>
<code>
<i>field_number</i><b>[</b>.<i>last_character</i><b>]
</b></code>
</pre>
<p>
The
<i>field_number</i>
is as described above for
<i>field_start.</i>
The
<i>last_character</i>
piece, interpreted as a non-negative decimal integer,
specifies the last character to be used as part of the sort key.
If
<i>last_character</i>
evaluates to zero or
<i>.last_character</i>
is omitted, it
refers to the last character of the field specified by
<i>field_number.</i>
<p>
If the
<b>-b</b>
option or
b
type modifier is in effect, characters within a
field are counted from the first
non-blank character
in the field.
(This applies separately to
<i>first_character</i>
and
<i>last_character</i>.)
<p>
The obsolescent options:
<pre>
<code>
<b>[</b>+<i>pos1</i><b>[</b>-<i>pos2</i><b>]]
</b></code>
</pre>
provide functionality equivalent to the
<b>-k</b>&nbsp;<i>keydef</i>
option.
For comparison, the full formats of these options are:
<pre>
<code>
+<i>field0_number</i><b>[</b>.<i>first0_character</i><b>][</b><i>type</i><b>]
    [</b>-<i>field0_number</i><b>[</b>.<i>first0_character</i><b>][</b><i>type</i><b>]]</b>
-k <i>field_number</i><b>[</b>.<i>first_character</i><b>][</b><i>type</i><b>]
    [</b>,<i>field_number</i><b>[</b>.<i>last_character</i><b>][</b><i>type</i><b>]]
</b></code>
</pre>
<p>
In the obsolescent form, fields (specified by
<i>field0_number</i>)
and characters within fields (specified by
<i>first0_character</i>)
are numbered from zero instead of one.
The optional type modifiers are the same in both forms.
If
<i>.first0_character</i>
is omitted or
<i>first0_character</i>
evaluates to zero, it refers to the first character of the field.
The
<b>-b</b>
option does not apply to
<i>-pos2</i>.
<p>
The fully specified
<i>+pos1</i>
<i>-pos2</i>
form with type modifiers
<i>T</i>
and
<i>U</i>:
<pre>
<code>
+<i>w</i>.<i>xT</i> -<i>y</i>.<i>zU</i>
</code>
</pre>
<br>
is equivalent to:
<pre>
<dl compact><dt> <dd>
<table <tr valign=top><th align=left><i>undefined</i>
<th align=left>(<i>z</i>==0 &amp; <i>U</i> contains b &amp; -t is present)
<tr valign=top><td align=left>-k <i>w</i>+1.<i>x</i>+1<i>T</i>,<i>y</i>.0<i>U</i>
<td align=left>(<i>z</i>==0 otherwise)
<tr valign=top><td align=left>-k <i>w</i>+1.<i>x</i>+1<i>T</i>,<i>y</i>+1.<i>zU</i>
<td align=left>(<i>z</i> &gt; 0)
</table>
</dl>
</pre>
<p>
As with the non-obsolescent forms, implementations support at least
nine occurrences of the
<i>+pos1</i>
option, which are significant in command line order.
</blockquote><h4><a name = "tag_001_014_2043">&nbsp;</a>EXIT STATUS</h4><blockquote>
The following exit values are returned:
<dl compact>

<dt>0<dd>All input files were output successfully,
or
<b>-c</b>
was specified and the input file was correctly sorted.

<dt>1<dd>Under the
<b>-c</b>
option, the file was not ordered
as specified, or
if the
<b>-c</b>
and
<b>-u</b>
options were both specified,
two input lines were found with equal keys.

<dt>&gt;1<dd>An error occurred.

</dl>
</blockquote><h4><a name = "tag_001_014_2044">&nbsp;</a>CONSEQUENCES OF ERRORS</h4><blockquote>
Default.
</blockquote><h4><a name = "tag_001_014_2045">&nbsp;</a>APPLICATION USAGE</h4><blockquote>
The default value for
<b>-t</b>,
blank character,
has different properties from, for example,
-t "&lt;space&gt;".
If a line contains:
<pre>
<code>
&lt;space&gt;&lt;space&gt;foo
</code>
</pre>
the following treatment would occur
with default separation as opposed to specifically selecting a
space character:
<br>
<p><table  bordercolor=#000000 border=1 align=center><tr valign=top><th align=center><b>Field</b>
<th align=center><b>Default</b>
<th align=center><b>-t "&lt;space&gt;"</b>
<tr valign=top><td align=left>1
<td align=left>&lt;space&gt;&lt;space&gt;foo
<td align=left><i>empty</i>
<tr valign=top><td align=left>2
<td align=left><i>empty</i>
<td align=left><i>empty</i>
<tr valign=top><td align=left>3
<td align=left><i>empty</i>
<td align=left>foo
</table>
<p>
The leading field separator itself is included in a field when
<b>-t</b>
is not used.
For example, this command returns an exit status
of zero, meaning the input was already sorted:
<pre>
<code>
sort -c -k 2 &lt;&lt;eof
y&lt;tab&gt;b
x&lt;space&gt;a
eof
</code>
</pre>
(assuming that a
tab character
precedes the
space character
in the current collating sequence).
The field separator is not included in a field when it
is explicitly set via
<b>-t</b>.
This is historical practice and allows usage such as:
<pre>
<code>
sort -t "|" -k 2n &lt;&lt;eof
Atlanta|425022|Georgia
Birmingham|284413|Alabama
Columbia|100385|South Carolina
eof
</code>
</pre>
where the second field can be correctly sorted numerically
without regard to the non-numeric field separator.
<p>
The wording in the OPTIONS section clarifies that the
<b>-b</b>,
<b>-d</b>,
<b>-f</b>,
<b>-i</b>,
<b>-n</b>
and
<b>-r</b>
options have to come before the first sort key specified if they are
intended to apply to all specified keys.
The way it is described in this
document matches historical practice, not historical documentation.
In the non-obsolescent versions, the results are unspecified if these options
are specified after a
<b>-k</b>
option.
<p>
The
<b>-f</b>
option might not work as expected in locales where there is not a
one-to-one mapping between an upper- and a lower-case letter.
</blockquote><h4><a name = "tag_001_014_2046">&nbsp;</a>EXAMPLES</h4><blockquote>
In the following examples, non-obsolescent and obsolescent ways of specifying
sort keys are given as an aid to understanding the relationship
between the two forms.
<ol>
<p>
<li>
Either of the following commands sorts the contents of
<b>infile</b>
with the second field as the sort key:
<pre>
<code>
  sort -k 2,2 infile
  sort +1 -2 infile.sE
</code>
</pre>
<p>
<li>
Either of the following commands sorts, in reverse order, the contents of
<b>infile1</b>
and
<b>infile2</b>,
placing the output in
<b>outfile</b>
and using the second
character of the second field as the sort key
(assuming that the first character of the
second field is the field separator):
<pre>
<code>
  sort -r -o outfile -k 2.2,2.2 infile1 infile2
  sort -r -o outfile +1.1 -1.2 infile1 infile2.sE
</code>
</pre>
<p>
<li>
Either of the following commands sorts the contents of
<b>infile1</b>
and
<b>infile2</b>
using the second
non-blank
character of the second
field as the sort key:
<pre>
<code>
  sort -k 2.2b,2.2b infile1 infile2
  sort +1.1b -1.2b  infile1 infile2.sE
</code>
</pre>
<p>
<li>
Either of the following commands prints the System&nbsp;V password file (user
database) sorted by the numeric user ID (the third colon-separated
field):
<pre>
<code>
  sort -t : -k 3,3n /etc/passwd
  sort -t : +2 -3n /etc/passwd.sE
</code>
</pre>
<p>
<li>
Either of the following commands prints the lines of the already sorted
file
<b>infile</b>,
suppressing all but one occurrence of lines having the
same third field:
<pre>
<code>
  sort -um -k 3.1,3.0 infile
  sort -um +2.0 -3.0 infile.sE
</code>
</pre>
<p>
</ol>
</blockquote><h4><a name = "tag_001_014_2047">&nbsp;</a>FUTURE DIRECTIONS</h4><blockquote>
None.
</blockquote><h4><a name = "tag_001_014_2048">&nbsp;</a>SEE ALSO</h4><blockquote>
<i><a href="comm.html">comm</a></i>,
<i><a href="join.html">join</a></i>,
<i><a href="uniq.html">uniq</a></i>,
the <b>XSH</b> specification description of
<i><a href="../xsh/toupper.html">toupper()</a></i>.
</blockquote><hr size=2 noshade>
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