getopts.html

来自「IEEE 1003.1-2003, Single Unix Specificat」· HTML 代码 · 共 384 行 · 第 1/2 页

<li>
<p>The invoking program name shall be identified in the message. The invoking program name shall be the value of the shell special
parameter 0 (see <a href="xcu_chap02.html#tag_02_05_02"><i>Special Parameters</i></a> ) at the time the <i>getopts</i> utility is
invoked. A name equivalent to:</p>

<pre>
<tt>basename "$0"
</tt>
</pre>

<p>may be used.</p>
</li>

<li>
<p>If an option is found that was not specified in <i>optstring</i>, this error is identified and the invalid option character
shall be identified in the message.</p>
</li>

<li>
<p>If an option requiring an option-argument is found, but an option-argument is not found, this error shall be identified and the
invalid option character shall be identified in the message.</p>
</li>
</ul>
</blockquote>

<h4><a name="tag_04_62_12"></a>OUTPUT FILES</h4>

<blockquote>
<p>None.</p>
</blockquote>

<h4><a name="tag_04_62_13"></a>EXTENDED DESCRIPTION</h4>

<blockquote>
<p>None.</p>
</blockquote>

<h4><a name="tag_04_62_14"></a>EXIT STATUS</h4>

<blockquote>
<p>The following exit values shall be returned:</p>

<dl compact>
<dt>&nbsp;0</dt>

<dd>An option, specified or unspecified by <i>optstring</i>, was found.</dd>

<dt>&gt;0</dt>

<dd>The end of options was encountered or an error occurred.</dd>
</dl>
</blockquote>

<h4><a name="tag_04_62_15"></a>CONSEQUENCES OF ERRORS</h4>

<blockquote>
<p>Default.</p>
</blockquote>

<hr>
<div class="box"><em>The following sections are informative.</em></div>

<h4><a name="tag_04_62_16"></a>APPLICATION USAGE</h4>

<blockquote>
<p>Since <i>getopts</i> affects the current shell execution environment, it is generally provided as a shell regular built-in. If
it is called in a subshell or separate utility execution environment, such as one of the following:</p>

<pre>
<tt>(getopts abc value "$@")
nohup getopts ...
find . -exec getopts ... \;
</tt>
</pre>

<p>it does not affect the shell variables in the caller's environment.</p>

<p>Note that shell functions share <i>OPTIND</i> with the calling shell even though the positional parameters are changed. If the
calling shell and any of its functions uses <i>getopts</i> to parse arguments, the results are unspecified.</p>
</blockquote>

<h4><a name="tag_04_62_17"></a>EXAMPLES</h4>

<blockquote>
<p>The following example script parses and displays its arguments:</p>

<pre>
<tt>aflag=
bflag=
while getopts ab: name
do
    case $name in
    a)    aflag=1;;
    b)    bflag=1
          bval="$OPTARG";;
    ?)   printf "Usage: %s: [-a] [-b value] args\n" $0
          exit 2;;
    esac
done
if [ ! -z "$aflag" ]; then
    printf "Option -a specified\n"
fi
if [ ! -z "$bflag" ]; then
    printf 'Option -b "%s" specified\n' "$bval"
fi
shift $(($OPTIND - 1))
printf "Remaining arguments are: %s\n" "$*"
</tt>
</pre>
</blockquote>

<h4><a name="tag_04_62_18"></a>RATIONALE</h4>

<blockquote>
<p>The <i>getopts</i> utility was chosen in preference to the System V <i>getopt</i> utility because <i>getopts</i> handles
option-arguments containing &lt;blank&gt;s.</p>

<p>The <i>OPTARG</i> variable is not mentioned in the ENVIRONMENT VARIABLES section because it does not affect the execution of
<i>getopts</i>; it is one of the few &quot;output-only&quot; variables used by the standard utilities.</p>

<p>The colon is not allowed as an option character because that is not historical behavior, and it violates the Utility Syntax
Guidelines. The colon is now specified to behave as in the KornShell version of the <i>getopts</i> utility; when used as the first
character in the <i>optstring</i> operand, it disables diagnostics concerning missing option-arguments and unexpected option
characters. This replaces the use of the <i>OPTERR</i> variable that was specified in an early proposal.</p>

<p>The formats of the diagnostic messages produced by the <i>getopts</i> utility and the <a href=
"../functions/getopt.html"><i>getopt</i>()</a> function are not fully specified because implementations with superior
(``friendlier&quot;) formats objected to the formats used by some historical implementations. The standard developers considered it
important that the information in the messages used be uniform between <i>getopts</i> and <a href=
"../functions/getopt.html"><i>getopt</i>()</a>. Exact duplication of the messages might not be possible, particularly if a utility
is built on another system that has a different <a href="../functions/getopt.html"><i>getopt</i>()</a> function, but the messages
must have specific information included so that the program name, invalid option character, and type of error can be distinguished
by a user.</p>

<p>Only a rare application program intercepts a <i>getopts</i> standard error message and wants to parse it. Therefore,
implementations are free to choose the most usable messages they can devise. The following formats are used by many historical
implementations:</p>

<pre>
<tt>"%s: illegal option -- %c\n", &lt;</tt><i>program name</i><tt>&gt;, &lt;</tt><i>option character</i><tt>&gt;
<br>
"%s: option requires an argument -- %c\n", &lt;</tt><i>program name</i><tt>&gt;, \
    &lt;</tt><i>option character</i><tt>&gt;
</tt>
</pre>

<p>Historical shells with built-in versions of <a href="../functions/getopt.html"><i>getopt</i>()</a> or <i>getopts</i> have used
different formats, frequently not even indicating the option character found in error.</p>
</blockquote>

<h4><a name="tag_04_62_19"></a>FUTURE DIRECTIONS</h4>

<blockquote>
<p>None.</p>
</blockquote>

<h4><a name="tag_04_62_20"></a>SEE ALSO</h4>

<blockquote>
<p><a href="xcu_chap02.html#tag_02_05_02"><i>Special Parameters</i></a> , the System Interfaces volume of
IEEE&nbsp;Std&nbsp;1003.1-2001, <a href="../functions/getopt.html"><i>getopt</i>()</a></p>
</blockquote>

<h4><a name="tag_04_62_21"></a>CHANGE HISTORY</h4>

<blockquote>
<p>First released in Issue 4.</p>
</blockquote>

<h4><a name="tag_04_62_22"></a>Issue 6</h4>

<blockquote>
<p>The normative text is reworded to avoid use of the term &quot;must&quot; for application requirements.</p>
</blockquote>

<div class="box"><em>End of informative text.</em></div>

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