📄 getopts.html

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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><html><head><!-- Copyright 1997 The Open Group, All Rights Reserved --><title>getopts</title></head><body bgcolor=white><center><font size=2>The Single UNIX &reg; Specification, Version 2<br>Copyright &copy; 1997 The Open Group</font></center><hr size=2 noshade><h4><a name = "tag_001_014_871">&nbsp;</a>NAME</h4><blockquote>getopts - parse utility options</blockquote><h4><a name = "tag_001_014_872">&nbsp;</a>SYNOPSIS</h4><blockquote><pre><code>getopts <i>optstring name </i><b>[</b><i>arg</i>...<b>]</b></code></pre></blockquote><h4><a name = "tag_001_014_873">&nbsp;</a>DESCRIPTION</h4><blockquote>The<i>getopts</i>utility can be used to retrieve options and option-argumentsfrom a list of parameters.It supports the utility argument syntaxguidelines 3 to 10, inclusive, described inthe <b>XBD</b> specification, <a href="../xbd/utilconv.html#usg"><b>Utility Syntax Guidelines</b>&nbsp;</a> .<p>Each time it is invoked, the<i>getopts</i>utility places the value of thenext option in the shell variablespecified by the<i>name</i>operand and theindex of the next argument to be processed in the shell variable<i>OPTIND .</i>Whenever the shell is invoked,<i>OPTIND</i>will be initialised to 1.<p>When the option requires an option-argument, the<i>getopts</i>utility will place it in the shell variable<i>OPTARG .</i>If no option was found, or if theoption that was found does not have an option-argument,<i>OPTARG</i>will be unset.<p>If an option character not contained in the<i>optstring</i>operand is foundwhere an option character is expected, the shell variable specified by<i>name</i>will be set to the question-mark(?)character.In this case, ifthe first character in<i>optstring</i>is a colon(:),the shell variable<i>OPTARG</i>will be set to the option character found,but no output will be written to standard error;otherwise, the shell variable<i>OPTARG</i>will be unset and a diagnostic message will bewritten to standard error.This condition is considered to be anerror detected in the way arguments were presented to the invoking application,but is not an error in<i>getopts</i>processing.<p>If an option-argument is missing:<ul><p><li>If the first character of<i>optstring</i>is a colon, the shell variablespecified by<i>name</i>will be set to the colon character and the shell variable<i>OPTARG</i>will be set to the option character found.<p><p><li>Otherwise, the shell variable specified by<i>name</i>will be set to thequestion-mark character, the shell variable<i>OPTARG</i>will be unset,and a diagnostic message will be written to standard error.This condition is considered to be an error detected in theway arguments were presented to the invoking application, butis not an error in<i>getopts</i>processing; a diagnostic messagewill be written as stated, but the exit status will be zero.<p></ul><p>When the end of options is encountered, the<i>getopts</i>utility will exitwith a return valuegreater than zero; the shell variable<i>OPTIND</i>will be set to theindex of the first non-option-argument,where the first--argument is considered to be an option-argument if there are no othernon-option-arguments appearing before it,or the value$#+ 1 if there are nonon-option-arguments; the<i>name</i>variable will be set to the question-markcharacter.Any of the followingidentifies the end of options:the special option--,finding an argument that does notbegin with a "-", or encountering an error.<p>The shell variables<i>OPTIND</i>and<i>OPTARG</i>are local to the caller of<i>getopts</i>and are not exported by default.<p>The shell variable specified by the<i>name</i>operand,<i>OPTIND</i>and<i>OPTARG</i>affect the current shell execution environment; see<xref href=shexenv><a href="chap2.html#tag_001_012">Shell Execution Environment</a></xref>.<p>If the application sets<i>OPTIND</i>to the value 1, a new set of parameters can be used:either the current positional parameters or new<i>arg</i>values.Any other attempt to invoke<i>getopts</i>multiple times in a single shell execution environment withparameters (positional parameters or<i>arg</i>operands) that are not the same in all invocations, or with an<i>OPTIND</i>value modified to be a value other than 1, produces unspecified results.</blockquote><h4><a name = "tag_001_014_874">&nbsp;</a>OPTIONS</h4><blockquote>None.</blockquote><h4><a name = "tag_001_014_875">&nbsp;</a>OPERANDS</h4><blockquote>The following operands are supported:<dl compact><dt><i>optstring</i><dd>A string containing the option charactersrecognised by the utility invoking<i>getopts</i>.If a character is followedby a colon, the option will be expected to have anargument, which should be supplied as a separate argument.Applications should specifyan option character and its option-argument as separate arguments,but<i>getopts</i>will interpret the characters following an optioncharacter requiring arguments as an argument whether or notthis is done.An explicit null option-argumentneed not be recognised if it is not supplied as aseparate argument when<i>getopts</i>is invoked.(See also the <b>XSH</b> specification<i><a href="../xsh/getopt.html">getopt()</a></i>function.)The characters question-mark and colonmust not be used as option characters by an application.The use of other option characters that are not alphanumericproduces unspecified results.If the option-argument is notsupplied as a separate argumentfrom the option character, the value in<i>OPTARG</i>will be stripped of the option character and the "-".The first character in<i>optstring</i>will determine how<i>getopts</i>will behave if an option character is not knownor an option-argument is missing.<dt><i>name</i><dd>The name of a shell variable that will be set by the<i>getopts</i>utility to the option character that was found.</dl><p>The<i>getopts</i>utility by default will parse positional parameters passedto the invoking shell procedure.If<i>arg</i>sare given, they will be parsed instead of the positional parameters.</blockquote><h4><a name = "tag_001_014_876">&nbsp;</a>STDIN</h4><blockquote>Not used.</blockquote><h4><a name = "tag_001_014_877">&nbsp;</a>INPUT FILES</h4><blockquote>None.</blockquote><h4><a name = "tag_001_014_878">&nbsp;</a>ENVIRONMENT VARIABLES</h4><blockquote>The following environment variables affect the execution of<i>getopts</i>:<dl compact><dt><i>LANG</i><dd>Provide a default value for the internationalisation variablesthat are unset or null.If<i>LANG</i>is unset or null, the corresponding value from theimplementation-dependent default locale will be used.If any of the internationalisation variables contains an invalid setting, theutility will behave as if none of the variables had been defined.<dt><i>LC_ALL</i><dd>If set to a non-empty string value,override the values of all the other internationalisation variables.<dt><i>LC_CTYPE</i><dd>Determine thelocale for the interpretation of sequences of bytes of text data ascharacters (for example, single- as opposed to multi-byte charactersin arguments and input files).<dt><i>LC_MESSAGES</i><dd>Determine the locale that should be used to affectthe format and contents of diagnosticmessages written to standard error.<dt><i>NLSPATH</i><dd>Determine the location of message cataloguesfor the processing of<i>LC_MESSAGES .</i><dt><i>OPTIND</i><dd>This variable will be used by the<i>getopts</i>utility as the index of the next argument to be processed.</dl></blockquote><h4><a name = "tag_001_014_879">&nbsp;</a>ASYNCHRONOUS EVENTS</h4><blockquote>Default.</blockquote><h4><a name = "tag_001_014_880">&nbsp;</a>STDOUT</h4><blockquote>Not used.</blockquote><h4><a name = "tag_001_014_881">&nbsp;</a>STDERR</h4><blockquote>Whenever an error is detectedand the first character in the<i>optstring</i>operand is not a colon(:),a diagnostic message will be written tostandard errorwith the following information in an unspecified format:<ul><p><li>The invoking program name will be identified in the message.The invoking programname will be the value of the shell special parameter0(see<xref href=specpar><a href="chap2.html#tag_001_005_002">Special Parameters</a></xref>)at the time the<i>getopts</i>utility is invoked.A name equivalent to:<pre><code>basename "$0"</code></pre>may be used.<p><li>If an option is found that was not specified in<i>optstring,</i>this error will be identified and the invalidoption character will be identified in the message.<p><li>If an option requiring an option-argument is found, but an option-argumentis not found,this error will be identified and the invalidoption character will be identified in the message.<p></ul></blockquote><h4><a name = "tag_001_014_882">&nbsp;</a>OUTPUT FILES</h4><blockquote>None.</blockquote><h4><a name = "tag_001_014_883">&nbsp;</a>EXTENDED DESCRIPTION</h4><blockquote>None.</blockquote><h4><a name = "tag_001_014_884">&nbsp;</a>EXIT STATUS</h4><blockquote>The following exit values are returned:<dl compact><dt>0<dd>An option, specified or unspecified by<i>optstring</i>,was found.<dt>&gt;0<dd>The end of options was encountered or an error occurred.</dl></blockquote><h4><a name = "tag_001_014_885">&nbsp;</a>CONSEQUENCES OF ERRORS</h4><blockquote>Default.</blockquote><h4><a name = "tag_001_014_886">&nbsp;</a>APPLICATION USAGE</h4><blockquote>Since<i>getopts</i>affects the current shell execution environment,it is generally provided as a shell regular built-in.If it is called in a subshell or separate utility execution environment,such as one of the following:<pre><code>(getopts abc value "$@")nohup getopts ...find . -exec getopts ... \;</code></pre>it will not affect the shell variables in the caller's environment.<p>Note that shell functions share<i>OPTIND</i>with the calling shell even thoughthe positional parameters are changed.Functions that want to use<i>getopts</i>to parse their arguments will usually want to save the value of<i>OPTIND</i>on entry and restore it before returning.However, there will becases when a function will want to change<i>OPTIND</i>for the calling shell.</blockquote><h4><a name = "tag_001_014_887">&nbsp;</a>EXAMPLES</h4><blockquote>The following example script parses and displays its arguments:<pre><code>aflag=bflag=while getopts ab: namedo    case $name in    a)    aflag=1;;    b)    bflag=1          bval="$OPTARG";;    )   printf "Usage: %s: [-a] [-b value] args\n" $0          exit 2;;    esacdoneif [ ! -z "$aflag" ]; then    printf "Option -a specified\n"fiif [ ! -z "$bflag" ]; then    printf 'Option -b "%s" specified\n' "$bval"fishift $(($OPTIND - 1))printf "Remaining arguments are: %s\n" "$*"</code></pre></blockquote><h4><a name = "tag_001_014_888">&nbsp;</a>FUTURE DIRECTIONS</h4><blockquote>None.</blockquote><h4><a name = "tag_001_014_889">&nbsp;</a>SEE ALSO</h4><blockquote>The <b>XSH</b> specification description of<i><a href="../xsh/getopt.html">getopt()</a></i>.</blockquote><hr size=2 noshade><center><font size=2>UNIX &reg; is a registered Trademark of The Open Group.<br>Copyright &copy; 1997 The Open Group<br> [ <a href="../index.html">Main Index</a> | <a href="../xshix.html">XSH</a> | <a href="../xcuix.html">XCU</a> | <a href="../xbdix.html">XBD</a> | <a href="../cursesix.html">XCURSES</a> | <a href="../xnsix.html">XNS</a> ]</font></center><hr size=2 noshade></body></html>
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