ch04_09.htm

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<dt><tt class="literal">%P</tt></dt><dd>Translate <tt class="literal">egrep</tt> extended regular expression
into <tt class="literal">ksh</tt> pattern.</p>
</dd>
<dt><tt class="literal">%q</tt></dt><dd>Print a quoted string that can


be reread later on.</p>
</dd>
</dl>

</td></tr>

<tr><td valign="top"><a name="pwd">pwd</a></a></td><td><p><tt class="literal">pwd</tt></p><p><tt class="literal">pwd</tt> [<tt class="literal">-LP</tt>]</p>
<p>
<a name="IXT-4-122869" />Print your present working directory on standard output.
The second form is specific to the Korn shell.</p>
<h4 class="refsect2">Options</h4><p>Options give control over the use of logical versus physical
treatment of the printed path.
See the entry for <b class="emphasis-bold"><a href="#cd">cd</a></b>, earlier in this section.</p>
<dl><dt><tt class="literal">-L</tt></dt><dd>Use logical path (what the user typed, including any symbolic links)
and the value of PWD for the current directory.
This is the default.</p>
</dd>
<dt><tt class="literal">-P</tt></dt><dd>Use the actual filesystem physical path
for the current directory.</p>
</dd>
</dl>

</td></tr><tr><td valign="top"><a name="r">r</a></a></td><td><tt class="literal">r</tt>
<p>
<a name="IXT-4-122870" />Reexecute previous command.
<tt class="literal">ksh88</tt> alias for <tt class="literal">fc -e -</tt>.
<tt class="literal">ksh93</tt> alias for <tt class="literal">hist -s</tt>.</p>
</td></tr><tr><td valign="top"><a name="read">read</a></a></td><td><tt class="literal">read</tt> <em class="replaceable"><tt>variable1</em> [<em class="replaceable">variable2 ...</tt></em>]
<p>
<a name="IXT-4-122871" />Read one line of standard input and assign each word to
the corresponding
<em class="emphasis">variable</em>, with all leftover words assigned to the last variable.  If
only one variable is specified, the entire line will be assigned to
that variable.  See the Examples here and under <tt class="literal">case</tt>.
The return status is 0 unless <em class="emphasis">EOF</em> is reached.</p>
<h4 class="refsect2">Example</h4><blockquote><pre class="code">$ <tt class="userinput"><b>read first last address</b></tt>
Sarah Caldwell 123 Main Street
$ <tt class="userinput"><b>echo "$last, $first\n$address"</b></tt>
<tt class="userinput"><b>Caldwell, Sarah
123 Main Street</b></tt></pre></blockquote>

</td></tr><tr><td valign="top"><a name="read">read</a></a></td><td><tt class="literal">read</tt> [<em class="replaceable"><tt>options</em>] [<em class="replaceable">variable1</em>[<tt class="literal">?</tt><em class="replaceable">string</em>]] [<em class="replaceable">variable2</tt></em> ...]
<p>
<a name="IXT-4-122872" />Korn shell only.  Same as in the Bourne shell, except that the Korn 
shell version
supports the following options as well as the <tt class="literal">?</tt> syntax for prompting.
If the first variable is followed by <tt class="literal">?</tt><em class="emphasis">string</em>,
<em class="emphasis">string</em> is displayed
as a user prompt.  If no variables are given, input is stored in the
REPLY variable.
Additionally, <tt class="literal">ksh93</tt> allows you to specify a
timeout.</p>
<h4 class="refsect2">Options</h4><dl><dt><tt class="literal">-A</tt> <tt><em class="replaceable">array</em></tt></dt><dd>Read into indexed array <em class="emphasis">array</em></tt>.
<tt class="literal">ksh93</tt> only.</p>
</dd>
<dt><tt class="literal">-d</tt> <tt><em class="replaceable">delim</em></tt></dt><dd>Read up to first occurrence of <em class="emphasis">delim</em></tt>,
instead of newline.
<tt class="literal">ksh93</tt> only.</p>
</dd>
<dt><tt class="literal">-p</tt></dt><dd>Read from the output of a <tt class="literal">|&amp;</tt> coprocess.</p>
</dd>
<dt><tt class="literal">-r</tt></dt><dd>Raw mode; ignore \ as a line continuation character.</p>
</dd>
<dt><tt class="literal">-s</tt></dt><dd>Save input as a command in the history file.</p>
</dd>
<dt><tt class="literal">-t</tt> <tt><em class="replaceable">timeout</em></tt></dt><dd>When reading from a terminal or pipe,
if no data is entered after <em class="emphasis">timeout</em> seconds,
return <tt class="literal">l</tt>.
This prevents an application from hanging forever, waiting for
user input.
<tt class="literal">ksh93</tt> only.</p>
</dd>
<dt><tt class="literal">-u</tt>[<tt><em class="replaceable">n</em></tt>]</dt><dd>Read input from file descriptor <em class="emphasis">n</em></tt> (default is 0).</p>
</dd>
</dl>

<h4 class="refsect2">Example</h4><p>Prompt yourself to enter two temperatures:</p>
<blockquote><pre class="code">$ <tt class="userinput"><b>read n1?"High low: " n2</b></tt>
High low: <tt class="userinput"><b>65 33</b></tt></pre></blockquote>

</td></tr><tr><td valign="top"><a name="readonly">readonly</a></a></td><td><tt class="literal">readonly</tt> [<tt><em class="replaceable"><tt>variable1 variable2</tt></em></tt> ...]<br><tt class="literal">readonly -p</tt>
<p>
<a name="IXT-4-122873" />Prevent the specified shell variables from being assigned new values.
Variables can be accessed (read) but not overwritten.
In the Korn shell, the syntax 
<em class="emphasis">variable</em></tt><tt class="literal">=</tt><em class="emphasis">value</em></tt> can
assign a new value that cannot be changed.
The second form is specific to <tt class="literal">ksh93</tt>.</p>
<h4 class="refsect2">Option</h4><dl><dt><tt class="literal">-p</tt></dt><dd>Print <tt class="literal">readonly</tt> before printing the
names and values of read-only variables.
This allows saving a list of read-only variables for rereading later.</p>
</dd>
</dl>

</td></tr><tr><td valign="top"><a name="redirect">redirect</a></a></td><td><tt class="literal">redirect</tt> <em class="replaceable"><tt>i/o-redirection</tt></em> ... 
<p><tt class="literal">ksh93</tt> alias for <tt class="literal">command exec</tt>.
<a name="IXT-4-122874" /></p>


<h4 class="refsect2">Example</h4><p>Change the shell's standard error to the console:</p>
<blockquote><pre class="code">$ <tt class="userinput"><b>redirect 2&gt;/dev/console</b></tt></pre></blockquote>

</td></tr><tr><td valign="top"><a name="return">return</a></a></td><td><tt class="literal">return</tt> [<em class="replaceable"><tt>n</tt></em>]
<p>
<a name="IXT-4-122875" />Use inside a function definition.
Exit the function with status <em class="emphasis">n</em> 
or with the exit status of the previously executed command.</p>
</td></tr><tr><td valign="top"><a name="select">select</a></a></td><td><tt class="literal">select</tt> <em class="replaceable"><tt>x</em> [<tt class="literal">in</tt> <em class="replaceable">list</em>]<br><tt class="literal">do</tt><br>&#160;&#160;&#160;&#160;<em class="replaceable">commands</tt></em><br><tt class="literal">done</tt>
<p>
<a name="IXT-4-122876" />Korn shell only.
Display a list of menu items on standard error, numbered in the
order they are specified in <em class="emphasis">list</em>.
If no <tt class="literal">in</tt> <em class="emphasis">list</em> is given,
items are taken from the command line (via
<tt class="literal">"$@"</tt>).
Following the menu is a prompt string (set by PS3).
At the PS3 prompt, users select a menu item by typing its
line number, or they redisplay the menu by pressing the Return key.  (User input is
stored in the shell variable REPLY.)
If a valid line number is typed, <em class="emphasis">commands</em> are executed.
Typing <em class="emphasis">EOF</em> terminates the loop.</p>
<h4 class="refsect2">Example</h4><blockquote><pre class="code">PS3="Select the item number: "
select event in Format Page View Exit
do
   case "$event" in
     Format) nroff $file | lp;;
     Page)   pr $file | lp;;
     View)   more $file;;
     Exit)   exit 0;;
     *   )   echo "Invalid selection";;
   esac
done</pre></blockquote>
<p>The output of this script looks like this:</p>
<blockquote><pre class="code">1. Format
2. Page
3. View
4. Exit
Select the item number:</pre></blockquote>

</td></tr><tr><td valign="top"><a name="set">set</a></a></td><td><tt class="literal">set</tt> [<em class="replaceable"><tt>options arg1 arg2 ...</tt></em>]
<p>
<a name="IXT-4-122877" />With no arguments, <tt class="literal">set</tt> prints the values of all variables
known to the current shell.  Options can be enabled
(<tt class="literal">-</tt><em class="emphasis">option</em>) or disabled (+<em class="emphasis">option</em>).
Options can also be set when the shell is invoked,
via <tt class="literal">ksh</tt> or <tt class="literal">sh</tt>.
(See the earlier <a href="ch04_07.htm#unut-ch-4-sect-7">Section 4.7</a>.) Arguments are assigned in order to <tt class="literal">$1</tt>,
<tt class="literal">$2</tt>, etc.</p>
<h4 class="refsect2">Options</h4><dl><dt><tt class="literal">+A</tt> <tt><em class="replaceable">name</em></tt></dt><dd>Assign remaining arguments as elements of array <em class="emphasis">name</em></tt>.  Korn
shell only.</p>
</dd>
<dt><tt class="literal">-A</tt> <tt><em class="replaceable">name</em></tt></dt><dd>Same as <tt class="literal">+A</tt>, but unset <em class="emphasis">name</em></tt> before making assignments.
Korn shell only.</p>
</dd>
<dt><tt class="literal">-a</tt></dt><dd>From now on automatically mark variables for export
after defining or changing them.</p>
</dd>
<dt><tt class="literal">-b</tt></dt><dd>Same as <tt class="literal">-o notify</tt>.
The single-letter form is only in <tt class="literal">ksh93</tt>.</p>
</dd>
<dt><tt class="literal">-C</tt></dt><dd>Same as <tt class="literal">-o noclobber</tt>.
The single-letter form is only in <tt class="literal">ksh93</tt>.</p>
</dd>
<dt><tt class="literal">-e</tt></dt><dd>Exit if a command yields a nonzero exit status.
In the Korn shell, the <tt class="literal">ERR</tt> trap is executed
before the shell exits.</p>
</dd>
<dt><tt class="literal">-f</tt></dt><dd>Ignore filename metacharacters (e.g., <tt class="literal">* ? [ ]</tt>).</p>
</dd>
<dt><tt class="literal">-h</tt></dt><dd>Locate commands as they are defined.  The Korn shell creates
tracked aliases, whereas the Bourne shell hashes command names.
See <b class="emphasis-bold"><a href="#hash">hash</a></b>.</p>
</dd>
<dt><tt class="literal">-k</tt></dt><dd>Assignment of environment variables (<em class="emphasis">var</em></tt><tt class="literal">=</tt><em class="emphasis">value</em></tt>) takes effect regardless of where they appear on the
command line.  Normally, assignments must precede the command name.</p>
</dd>
<dt><tt class="literal">-m</tt></dt><dd>Enable job control; background jobs execute in a separate process
group.  <tt class="literal">-m</tt> is usually set automatically.  Korn
shell only.</p>
</dd>
<dt><tt class="literal">-n</tt></dt><dd>Read commands but don't execute; useful for checking syntax.
The Korn shell ignores this option if it is interactive.</p>
</dd>
<dt><tt class="literal">-o</tt> [<tt><em class="replaceable">mode</em></tt>]</dt><dd>List Korn shell modes, or turn on mode <em class="emphasis">mode</em></tt>.
Many modes can be set by other options.  Modes are:
</p></dd>
</dl>

<table border="1" cellpadding="3">

<tr><td><tt class="literal">allexport</tt></td><td><p>Same as <tt class="literal">-a</tt>.</p>
</td></tr>
<tr><td><tt class="literal">bgnice</tt></td><td><p>Run background jobs at lower priority.</p>
</td></tr>
<tr><td><tt class="literal">emacs</tt></td><td><p>Set command-line editor to <tt class="literal">emacs</tt>.</p>
</td></tr>
<tr><td><tt class="literal">errexit</tt></td><td><p>Same as <tt class="literal">-e</tt>.</p>
</td></tr>
<tr><td><tt class="literal">ignoreeof</tt></td><td><p>Don't process <em class="emphasis">EOF</em> signals.
To exit the shell, type <tt class="literal">exit</tt>.</p>
</td></tr>
<tr><td><tt class="literal">keyword</tt></td><td><p>Same as <tt class="literal">-k</tt>.</p>
</td></tr>
<tr><td><tt class="literal">markdirs</tt></td><td><p>Append / to directory names.</p>
</td></tr>
<tr><td><tt class="literal">monitor</tt></td><td><p>Same as <tt class="literal">-m</tt>.</p>
</td></tr>
<tr><td><tt class="literal">noclobber</tt></td><td><p>Prevent overwriting via <tt class="literal">&gt;</tt> redirection;
use <tt class="literal">&gt;|</tt> to overwrite files.</p>
</td></tr>
<tr><td><tt class="literal">noexec</tt></td><td><p>Same as <tt class="literal">-n</tt>.</p>
</td></tr>
<tr><td><tt class="literal">noglob</tt></td><td><p>Same as <tt class="literal">-f</tt>.</p>
</td></tr>
<tr><td><tt class="literal">nolog</tt></td><td><p>Omit function definitions from history file.</p>
</td></tr>
<tr><td><tt class="literal">notify</tt></td><