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1539 lines
71 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html><head><title>CommandLine 2.0 Library Manual</title></head>
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<body bgcolor=white>
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<table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
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<tr><td> <font size=+3 color="#EEEEFF" face="Georgia,Palatino,Times,Roman"><b>CommandLine 2.0 Library Manual</b></font></td>
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</tr></table>
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<ol>
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<li><a href="#introduction">Introduction</a>
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<li><a href="#quickstart">Quick Start Guide</a>
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<ol>
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<li><a href="#bool">Boolean Arguments</a>
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<li><a href="#alias">Argument Aliases</a>
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<li><a href="#onealternative">Selecting an alternative from a
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set of possibilities</a>
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<li><a href="#namedalternatives">Named alternatives</a>
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<li><a href="#list">Parsing a list of options</a>
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<li><a href="#description">Adding freeform text to help output</a>
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</ol>
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<li><a href="#referenceguide">Reference Guide</a>
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<ol>
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<li><a href="#positional">Positional Arguments</a>
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<ul>
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<li><a href="#--">Specifying positional options with hyphens</a>
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<li><a href="#cl::ConsumeAfter">The <tt>cl::ConsumeAfter</tt>
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modifier</a>
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</ul>
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<li><a href="#storage">Internal vs External Storage</a>
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<li><a href="#attributes">Option Attributes</a>
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<li><a href="#modifiers">Option Modifiers</a>
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<ul>
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<li><a href="#hiding">Hiding an option from <tt>--help</tt> output</a>
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<li><a href="#numoccurances">Controlling the number of occurances
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required and allowed</a>
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<li><a href="#valrequired">Controlling whether or not a value must be
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specified</a>
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<li><a href="#formatting">Controlling other formatting options</a>
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<li><a href="#misc">Miscellaneous option modifiers</a>
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</ul>
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<li><a href="#toplevel">Top-Level Classes and Functions</a>
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<ul>
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<li><a href="#cl::ParseCommandLineOptions">The
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<tt>cl::ParseCommandLineOptions</tt> function</a>
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<li><a href="#cl::ParseEnvironmentOptions">The
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<tt>cl::ParseEnvironmentOptions</tt> function</a>
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<li><a href="#cl::opt">The <tt>cl::opt</tt> class</a>
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<li><a href="#cl::list">The <tt>cl::list</tt> class</a>
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<li><a href="#cl::alias">The <tt>cl::alias</tt> class</a>
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</ul>
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<li><a href="#builtinparsers">Builtin parsers</a>
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<ul>
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<li><a href="#genericparser">The Generic <tt>parser<t></tt>
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parser</a>
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<li><a href="#boolparser">The <tt>parser<bool></tt>
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specialization</a>
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<li><a href="#stringparser">The <tt>parser<string></tt>
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specialization</a>
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<li><a href="#intparser">The <tt>parser<int></tt>
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specialization</a>
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<li><a href="#doubleparser">The <tt>parser<double></tt> and
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<tt>parser<float></tt> specializations</a>
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</ul>
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</ol>
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<li><a href="#extensionguide">Extension Guide</a>
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<ol>
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<li><a href="#customparser">Writing a custom parser</a>
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<li><a href="#explotingexternal">Exploiting external storage</a>
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<li><a href="#dynamicopts">Dynamically adding command line options</a>
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</ol>
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<p><b>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a></b><p>
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</ol><p>
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<!-- *********************************************************************** -->
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<table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
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<tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
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<a name="introduction">Introduction
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</b></font></td></tr></table><ul>
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<!-- *********************************************************************** -->
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This document describes the CommandLine argument processing library. It will
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show you how to use it, and what it can do. The CommandLine library uses a
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declarative approach to specifying the command line options that your program
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takes. By default, these options declarations implicitly hold the value parsed
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for the option declared (of course this <a href="#storage">can be
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changed</a>).<p>
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Although there are a <b>lot</b> of command line argument parsing libraries out
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there in many different languages, none of them fit well with what I needed. By
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looking at the features and problems of other libraries, I designed the
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CommandLine library to have the following features:<p>
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<ol>
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<li>Speed: The CommandLine library is very quick and uses little resources. The
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parsing time of the library is directly proportional to the number of arguments
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parsed, not the the number of options recognized. Additionally, command line
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argument values are captured transparently into user defined global variables,
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which can be accessed like any other variable (and with the same
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performance).<p>
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<li>Type Safe: As a user of CommandLine, you don't have to worry about
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remembering the type of arguments that you want (is it an int? a string? a
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bool? an enum?) and keep casting it around. Not only does this help prevent
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error prone constructs, it also leads to dramatically cleaner source code.<p>
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<li>No subclasses required: To use CommandLine, you instantiate variables that
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correspond to the arguments that you would like to capture, you don't subclass a
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parser. This means that you don't have to write <b>any</b> boilerplate code.<p>
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<li>Globally accessible: Libraries can specify command line arguments that are
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automatically enabled in any tool that links to the library. This is possible
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because the application doesn't have to keep a "list" of arguments to pass to
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the parser. This also makes supporting <a href="#dynamicopts">dynamically
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loaded options</a> trivial.<p>
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<li>Cleaner: CommandLine supports enum and other types directly, meaning that
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there is less error and more security built into the library. You don't have to
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worry about whether your integral command line argument accidentally got
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assigned a value that is not valid for your enum type.<p>
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<li>Powerful: The CommandLine library supports many different types of
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arguments, from simple <a href="#boolparser">boolean flags</a> to <a
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href="#cl::opt">scalars arguments</a> (<a href="#stringparser">strings</a>, <a
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href="#intparser">integers</a>, <a href="#genericparser">enums</a>, <a
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href="#doubleparser">doubles</a>), to <a href="#cl::list">lists of
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arguments</a>. This is possible because CommandLine is...<p>
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<li>Extensible: It is very simple to add a new argument type to CommandLine.
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Simply specify the parser that you want to use with the command line option when
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you declare it. <a href="#customparser">Custom parsers</a> are no problem.<p>
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<li>Labor Saving: The CommandLine library cuts down on the amount of grunt work
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that you, the user, have to do. For example, it automatically provides a
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<tt>--help</tt> option that shows the available command line options for your
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tool. Additionally, it does most of the basic correctness checking for you.<p>
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<li>Capable: The CommandLine library can handle lots of different forms of
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options often found in real programs. For example, <a
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href="#positional">positional</a> arguments, <tt>ls</tt> style <a
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href="#cl::Grouping">grouping</a> options (to allow processing '<tt>ls
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-lad</tt>' naturally), <tt>ld</tt> style <a href="#cl::Prefix">prefix</a>
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options (to parse '<tt>-lmalloc -L/usr/lib</tt>'), and <a
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href="#cl::ConsumeAfter">interpreter style options</a>.<p>
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</ol>
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This document will hopefully let you jump in and start using CommandLine in your
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utility quickly and painlessly. Additionally it should be a simple reference
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manual to figure out how stuff works. If it is failing in some area (or you
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want an extension to the library), nag the author, <a
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href="mailto:sabre@nondot.org">Chris Lattner</a>.<p>
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<!-- *********************************************************************** -->
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</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0><tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
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<a name="quickstart">Quick Start Guide
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</b></font></td></tr></table><ul>
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<!-- *********************************************************************** -->
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This section of the manual runs through a simple CommandLine'ification of a
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basic compiler tool. This is intended to show you how to jump into using the
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CommandLine library in your own program, and show you some of the cool things it
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can do.<p>
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To start out, you need to include the CommandLine header file into your
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program:<p>
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<pre>
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#include "Support/CommandLine.h"
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</pre><p>
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Additionally, you need to add this as the first line of your main program:<p>
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<pre>
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int main(int argc, char **argv) {
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<a href="#cl::ParseCommandLineOptions">cl::ParseCommandLineOptions</a>(argc, argv);
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...
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}
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</pre><p>
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... which actually parses the arguments and fills in the variable
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declarations.<p>
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Now that you are ready to support command line arguments, we need to tell the
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system which ones we want, and what type of argument they are. The CommandLine
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library uses a declarative syntax to model command line arguments with the
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global variable declarations that capture the parsed values. This means that
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for every command line option that you would like to support, there should be a
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global variable declaration to capture the result. For example, in a compiler,
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we would like to support the unix standard '<tt>-o <filename></tt>' option
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to specify where to put the output. With the CommandLine library, this is
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represented like this:<p>
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<pre><a name="value_desc_example">
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<a href="#cl::opt">cl::opt</a><string> OutputFilename("<i>o</i>", <a href="#cl::desc">cl::desc</a>("<i>Specify output filename</i>"), <a href="#cl::value_desc">cl::value_desc</a>("<i>filename</i>"));
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</pre><p>
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This declares a global variable "<tt>OutputFilename</tt>" that is used to
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capture the result of the "<tt>o</tt>" argument (first parameter). We specify
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that this is a simple scalar option by using the "<tt><a
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href="#cl::opt">cl::opt</a></tt>" template (as opposed to the <a
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href="#list">"<tt>cl::list</tt> template</a>), and tell the CommandLine library
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that the data type that we are parsing is a string.<p>
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The second and third parameters (which are optional) are used to specify what to
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output for the "<tt>--help</tt>" option. In this case, we get a line that looks
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like this:<p>
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<pre>
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USAGE: compiler [options]
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OPTIONS:
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-help - display available options (--help-hidden for more)
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<b>-o <filename> - Specify output filename</b>
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</pre>
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Because we specified that the command line option should parse using the
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<tt>string</tt> data type, the variable declared is automatically usable as a
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real string in all contexts that a normal C++ string object may be used. For
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example:<p>
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<pre>
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...
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ofstream Output(OutputFilename.c_str());
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if (Out.good()) ...
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...
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</pre><p>
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There are many different options that you can use to customize the command line
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option handling library, but the above example shows the general interface to
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these options. The options can be specified in any order, and are specified
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with helper functions like <a href="#cl::desc"><tt>cl::desc(...)</tt></a>, so
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there are no positional dependencies to remember. The available options are
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discussed in detail in the <a href="#referenceguide">Reference Guide</a>.<p>
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Continuing the example, we would like to have our compiler take an input
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filename as well as an output filename, but we do not want the input filename to
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be specified with a hyphen (ie, not <tt>-filename.c</tt>). To support this
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style of argument, the CommandLine library allows for <a
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href="#positional">positional</a> arguments to be specified for the program.
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These positional arguments are filled with command line parameters that are not
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in option form. We use this feature like this:<p>
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<pre>
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<a href="#cl::opt">cl::opt</a><string> InputFilename(<a href="#cl::Positional">cl::Positional</a>, <a href="#cl::desc">cl::desc</a>("<i><input file></i>"), <a href="#cl::init">cl::init</a>("<i>-</i>"));
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</pre>
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This declaration indicates that the first positional argument should be treated
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as the input filename. Here we use the <tt><a
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href="#cl::init">cl::init</a></tt> option to specify an initial value for the
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command line option, which is used if the option is not specified (if you do not
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specify a <tt><a href="#cl::init">cl::init</a></tt> modifier for an option, then
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the default constructor for the data type is used to initialize the value).
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Command line options default to being optional, so if we would like to require
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that the user always specify an input filename, we would add the <tt><a
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href="#cl::Required">cl::Required</a></tt> flag, and we could eliminate the
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<tt><a href="#cl::init">cl::init</a></tt> modifier, like this:<p>
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<pre>
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<a href="#cl::opt">cl::opt</a><string> InputFilename(<a href="#cl::Positional">cl::Positional</a>, <a href="#cl::desc">cl::desc</a>("<i><input file></i>"), <b><a href="#cl::Required">cl::Required</a></b>);
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</pre>
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Again, the CommandLine library does not require the options to be specified in
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any particular order, so the above declaration is equivalent to:<p>
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<pre>
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<a href="#cl::opt">cl::opt</a><string> InputFilename(<a href="#cl::Positional">cl::Positional</a>, <a href="#cl::Required">cl::Required</a>, <a href="#cl::desc">cl::desc</a>("<i><input file></i>"));
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</pre>
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By simply adding the <tt><a href="#cl::Required">cl::Required</a></tt> flag, the
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CommandLine library will automatically issue an error if the argument is not
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specified, which shifts all of the command line option verification code out of
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your application into the library. This is just one example of how using flags
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can alter the default behaviour of the library, on a per-option basis. By
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adding one of the declarations above, the <tt>--help</tt> option synopsis is now
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extended to:<p>
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<pre>
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USAGE: compiler [options] <b><input file></b>
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OPTIONS:
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-help - display available options (--help-hidden for more)
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-o <filename> - Specify output filename
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</pre>
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... indicating that an input filename is expected.<p>
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<!-- ======================================================================= -->
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</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0><tr><td> </td><td width="100%"> <font color="#EEEEFF" face="Georgia,Palatino"><b>
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<a name="bool">Boolean Arguments
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</b></font></td></tr></table><ul>
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In addition to input and output filenames, we would like the compiler example to
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support three boolean flags: "<tt>-f</tt>" to force overwriting of the output
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file, "<tt>--quiet</tt>" to enable quiet mode, and "<tt>-q</tt>" for backwards
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compatibility with some of our users. We can support these by declaring options
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of boolean type like this:<p>
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<pre>
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<a href="#cl::opt">cl::opt</a><bool> Force ("<i>f</i>", <a href="#cl::desc">cl::desc</a>("<i>Overwrite output files</i>"));
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<a href="#cl::opt">cl::opt</a><bool> Quiet ("<i>quiet</i>", <a href="#cl::desc">cl::desc</a>("<i>Don't print informational messages</i>"));
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<a href="#cl::opt">cl::opt</a><bool> Quiet2("<i>q</i>", <a href="#cl::desc">cl::desc</a>("<i>Don't print informational messages</i>"), <a href="#cl::Hidden">cl::Hidden</a>);
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</pre><p>
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This does what you would expect: it declares three boolean variables
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("<tt>Force</tt>", "<tt>Quiet</tt>", and "<tt>Quiet2</tt>") to recognize these
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options. Note that the "<tt>-q</tt>" option is specified with the "<a
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href="#cl::Hidden"><tt>cl::Hidden</tt></a>" flag. This modifier prevents it
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from being shown by the standard "<tt>--help</tt>" output (note that it is still
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shown in the "<tt>--help-hidden</tt>" output).<p>
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The CommandLine library uses a <a href="#builtinparsers">different parser</a>
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for different data types. For example, in the string case, the argument passed
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to the option is copied literally into the content of the string variable... we
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obviously cannot do that in the boolean case, however, so we must use a smarter
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parser. In the case of the boolean parser, it allows no options (in which case
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it assigns the value of true to the variable), or it allows the values
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"<tt>true</tt>" or "<tt>false</tt>" to be specified, allowing any of the
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following inputs:<p>
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<pre>
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compiler -f # No value, 'Force' == true
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compiler -f=true # Value specified, 'Force' == true
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compiler -f=TRUE # Value specified, 'Force' == true
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compiler -f=FALSE # Value specified, 'Force' == false
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</pre>
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... you get the idea. The <a href="#boolparser">bool parser</a> just turns the
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string values into boolean values, and rejects things like '<tt>compiler
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-f=foo</tt>'. Similarly, the <a href="#doubleparser">float</a>, <a
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href="#doubleparser">double</a>, and <a href="#intparser">int</a> parsers work
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like you would expect, using the '<tt>strtol</tt>' and '<tt>strtod</tt>' C
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library calls to parse the string value into the specified data type.<p>
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With the declarations above, "<tt>compiler --help</tt>" emits this:<p>
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<pre>
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USAGE: compiler [options] <input file>
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OPTIONS:
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<b>-f - Overwrite output files</b>
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-o - Override output filename
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<b>-quiet - Don't print informational messages</b>
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-help - display available options (--help-hidden for more)
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</pre><p>
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and "<tt>opt --help-hidden</tt>" prints this:<p>
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<pre>
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USAGE: compiler [options] <input file>
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OPTIONS:
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-f - Overwrite output files
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-o - Override output filename
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<b>-q - Don't print informational messages</b>
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-quiet - Don't print informational messages
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-help - display available options (--help-hidden for more)
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</pre><p>
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This brief example has shown you how to use the '<tt><a
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href="#cl::opt">cl::opt</a></tt>' class to parse simple scalar command line
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arguments. In addition to simple scalar arguments, the CommandLine library also
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provides primitives to support CommandLine option <a href="#alias">aliases</a>,
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and <a href="#list">lists</a> of options.<p>
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|
|
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<!-- ======================================================================= -->
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</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0><tr><td> </td><td width="100%"> <font color="#EEEEFF" face="Georgia,Palatino"><b>
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<a name="alias">Argument Aliases
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</b></font></td></tr></table><ul>
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So far, the example works well, except for the fact that we need to check the
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quiet condition like this now:<p>
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<pre>
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...
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if (!Quiet && !Quiet2) printInformationalMessage(...);
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...
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</pre><p>
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... which is a real pain! Instead of defining two values for the same
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condition, we can use the "<tt><a href="#cl::alias">cl::alias</a></tt>" class to make the "<tt>-q</tt>"
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option an <b>alias</b> for the "<tt>-quiet</tt>" option, instead of providing
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a value itself:<p>
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<pre>
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<a href="#cl::opt">cl::opt</a><bool> Force ("<i>f</i>", <a href="#cl::desc">cl::desc</a>("<i>Overwrite output files</i>"));
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<a href="#cl::opt">cl::opt</a><bool> Quiet ("<i>quiet</i>", <a href="#cl::desc">cl::desc</a>("<i>Don't print informational messages</i>"));
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<a href="#cl::alias">cl::alias</a> QuietA("<i>q</i>", <a href="#cl::desc">cl::desc</a>("<i>Alias for -quiet</i>"), <a href="#cl::aliasopt">cl::aliasopt</a>(Quiet));
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</pre><p>
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The third line (which is the only one we modified from above) defines a
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"<tt>-q</tt> alias that updates the "<tt>Quiet</tt>" variable (as specified by
|
|
the <tt><a href="#cl::aliasopt">cl::aliasopt</a></tt> modifier) whenever it is
|
|
specified. Because aliases do not hold state, the only thing the program has to
|
|
query is the <tt>Quiet</tt> variable now. Another nice feature of aliases is
|
|
that they automatically hide themselves from the <tt>-help</tt> output
|
|
(although, again, they are still visible in the <tt>--help-hidden
|
|
output</tt>).<p>
|
|
|
|
Now the application code can simply use:<p>
|
|
|
|
<pre>
|
|
...
|
|
if (!Quiet) printInformationalMessage(...);
|
|
...
|
|
</pre><p>
|
|
|
|
... which is much nicer! The "<tt><a href="#cl::alias">cl::alias</a></tt>" can be used to specify an
|
|
alternative name for any variable type, and has many uses.<p>
|
|
|
|
|
|
|
|
<!-- ======================================================================= -->
|
|
</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0><tr><td> </td><td width="100%"> <font color="#EEEEFF" face="Georgia,Palatino"><b>
|
|
<a name="onealternative">Selecting an alternative from a set of possibilities
|
|
</b></font></td></tr></table><ul>
|
|
|
|
So far, we have seen how the CommandLine library handles builtin types like
|
|
<tt>std::string</tt>, <tt>bool</tt> and <tt>int</tt>, but how does it handle
|
|
things it doesn't know about, like enums or '<tt>int*</tt>'s?<p>
|
|
|
|
The answer is that it uses a table driven generic parser (unless you specify
|
|
your own parser, as described in the <a href="#extensionguide">Extension
|
|
Guide</a>). This parser maps literal strings to whatever type is required, are
|
|
requires you to tell it what this mapping should be.<p>
|
|
|
|
Lets say that we would like to add four optimizations levels to our optimizer,
|
|
using the standard flags "<tt>-g</tt>", "<tt>-O0</tt>", "<tt>-O1</tt>", and
|
|
"<tt>-O2</tt>". We could easily implement this with boolean options like above,
|
|
but there are several problems with this strategy:<p>
|
|
|
|
<ol>
|
|
<li>A user could specify more than one of the options at a time, for example,
|
|
"<tt>opt -O3 -O2</tt>". The CommandLine library would not be able to catch this
|
|
erroneous input for us.
|
|
|
|
<li>We would have to test 4 different variables to see which ones are set.
|
|
|
|
<li>This doesn't map to the numeric levels that we want... so we cannot easily
|
|
see if some level >= "<tt>-O1</tt>" is enabled.
|
|
|
|
</ol><p>
|
|
|
|
To cope with these problems, we can use an enum value, and have the CommandLine
|
|
library fill it in with the appropriate level directly, which is used like
|
|
this:<p>
|
|
|
|
<pre>
|
|
enum OptLevel {
|
|
g, O1, O2, O3
|
|
};
|
|
|
|
<a href="#cl::opt">cl::opt</a><OptLevel> OptimizationLevel(<a href="#cl::desc">cl::desc</a>("<i>Choose optimization level:</i>"),
|
|
<a href="#cl::values">cl::values</a>(
|
|
clEnumVal(g , "<i>No optimizations, enable debugging</i>"),
|
|
clEnumVal(O1, "<i>Enable trivial optimizations</i>"),
|
|
clEnumVal(O2, "<i>Enable default optimizations</i>"),
|
|
clEnumVal(O3, "<i>Enable expensive optimizations</i>"),
|
|
0));
|
|
|
|
...
|
|
if (OptimizationLevel >= O2) doPartialRedundancyElimination(...);
|
|
...
|
|
</pre><p>
|
|
|
|
This declaration defines a variable "<tt>OptimizationLevel</tt>" of the
|
|
"<tt>OptLevel</tt>" enum type. This variable can be assigned any of the values
|
|
that are listed in the declaration (Note that the declaration list must be
|
|
terminated with the "<tt>0</tt>" argument!). The CommandLine library enforces
|
|
that the user can only specify one of the options, and it ensure that only valid
|
|
enum values can be specified. The "<tt>clEnumVal</tt>" macros ensure that the
|
|
command line arguments matched the enum values. With this option added, our
|
|
help output now is:<p>
|
|
|
|
<pre>
|
|
USAGE: compiler [options] <input file>
|
|
|
|
OPTIONS:
|
|
<b>Choose optimization level:
|
|
-g - No optimizations, enable debugging
|
|
-O1 - Enable trivial optimizations
|
|
-O2 - Enable default optimizations
|
|
-O3 - Enable expensive optimizations</b>
|
|
-f - Overwrite output files
|
|
-help - display available options (--help-hidden for more)
|
|
-o <filename> - Specify output filename
|
|
-quiet - Don't print informational messages
|
|
</pre>
|
|
|
|
In this case, it is sort of awkward that flag names correspond directly to enum
|
|
names, because we probably don't want a enum definition named "<tt>g</tt>" in
|
|
our program. Because of this, we can alternatively write this example like
|
|
this:<p>
|
|
|
|
<pre>
|
|
enum OptLevel {
|
|
Debug, O1, O2, O3
|
|
};
|
|
|
|
<a href="#cl::opt">cl::opt</a><OptLevel> OptimizationLevel(<a href="#cl::desc">cl::desc</a>("<i>Choose optimization level:</i>"),
|
|
<a href="#cl::values">cl::values</a>(
|
|
clEnumValN(Debug, "g", "<i>No optimizations, enable debugging</i>"),
|
|
clEnumVal(O1 , "<i>Enable trivial optimizations</i>"),
|
|
clEnumVal(O2 , "<i>Enable default optimizations</i>"),
|
|
clEnumVal(O3 , "<i>Enable expensive optimizations</i>"),
|
|
0));
|
|
|
|
...
|
|
if (OptimizationLevel == Debug) outputDebugInfo(...);
|
|
...
|
|
</pre><p>
|
|
|
|
By using the "<tt>clEnumValN</tt>" macro instead of "<tt>clEnumVal</tt>", we can
|
|
directly specify the name that the flag should get. In general a direct mapping
|
|
is nice, but sometimes you can't or don't want to preserve the mapping, which is
|
|
when you would use it.<p>
|
|
|
|
|
|
|
|
<!-- ======================================================================= -->
|
|
</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0><tr><td> </td><td width="100%"> <font color="#EEEEFF" face="Georgia,Palatino"><b>
|
|
<a name="namedalternatives">Named Alternatives
|
|
</b></font></td></tr></table><ul>
|
|
|
|
Another useful argument form is a named alternative style. We shall use this
|
|
style in our compiler to specify different debug levels that can be used.
|
|
Instead of each debug level being its own switch, we want to support the
|
|
following options, of which only one can be specified at a time:
|
|
"<tt>--debug-level=none</tt>", "<tt>--debug-level=quick</tt>",
|
|
"<tt>--debug-level=detailed</tt>". To do this, we use the exact same format as
|
|
our optimization level flags, but we also specify an option name. For this
|
|
case, the code looks like this:<p>
|
|
|
|
<pre>
|
|
enum DebugLev {
|
|
nodebuginfo, quick, detailed
|
|
};
|
|
|
|
// Enable Debug Options to be specified on the command line
|
|
<a href="#cl::opt">cl::opt</a><DebugLev> DebugLevel("<i>debug_level</i>", <a href="#cl::desc">cl::desc</a>("<i>Set the debugging level:</i>"),
|
|
<a href="#cl::values">cl::values</a>(
|
|
clEnumValN(nodebuginfo, "none", "<i>disable debug information</i>"),
|
|
clEnumVal(quick, "<i>enable quick debug information</i>"),
|
|
clEnumVal(detailed, "<i>enable detailed debug information</i>"),
|
|
0));
|
|
</pre>
|
|
|
|
This definition defines an enumerated command line variable of type "<tt>enum
|
|
DebugLev</tt>", which works exactly the same way as before. The difference here
|
|
is just the interface exposed to the user of your program and the help output by
|
|
the "<tt>--help</tt>" option:<p>
|
|
|
|
<pre>
|
|
USAGE: compiler [options] <input file>
|
|
|
|
OPTIONS:
|
|
Choose optimization level:
|
|
-g - No optimizations, enable debugging
|
|
-O1 - Enable trivial optimizations
|
|
-O2 - Enable default optimizations
|
|
-O3 - Enable expensive optimizations
|
|
<b>-debug_level - Set the debugging level:
|
|
=none - disable debug information
|
|
=quick - enable quick debug information
|
|
=detailed - enable detailed debug information</b>
|
|
-f - Overwrite output files
|
|
-help - display available options (--help-hidden for more)
|
|
-o <filename> - Specify output filename
|
|
-quiet - Don't print informational messages
|
|
</pre><p>
|
|
|
|
Again, the only structural difference between the debug level declaration and
|
|
the optimiation level declaration is that the debug level declaration includes
|
|
an option name (<tt>"debug_level"</tt>), which automatically changes how the
|
|
library processes the argument. The CommandLine library supports both forms so
|
|
that you can choose the form most appropriate for your application.<p>
|
|
|
|
|
|
|
|
<!-- ======================================================================= -->
|
|
</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0><tr><td> </td><td width="100%"> <font color="#EEEEFF" face="Georgia,Palatino"><b>
|
|
<a name="list">Parsing a list of options
|
|
</b></font></td></tr></table><ul>
|
|
|
|
Now that we have the standard run of the mill argument types out of the way,
|
|
lets get a little wild and crazy. Lets say that we want our optimizer to accept
|
|
a <b>list</b> of optimizations to perform, allowing duplicates. For example, we
|
|
might want to run: "<tt>compiler -dce -constprop -inline -dce -strip</tt>". In
|
|
this case, the order of the arguments and the number of appearances is very
|
|
important. This is what the "<tt><a href="#cl::list">cl::list</a></tt>"
|
|
template is for. First, start by defining an enum of the optimizations that you
|
|
would like to perform:<p>
|
|
|
|
<pre>
|
|
enum Opts {
|
|
// 'inline' is a C++ keyword, so name it 'inlining'
|
|
dce, constprop, inlining, strip
|
|
};
|
|
</pre><p>
|
|
|
|
Then define your "<tt><a href="#cl::list">cl::list</a></tt>" variable:<p>
|
|
|
|
<pre>
|
|
<a href="#cl::list">cl::list</a><Opts> OptimizationList(<a href="#cl::desc">cl::desc</a>("<i>Available Optimizations:</i>"),
|
|
<a href="#cl::values">cl::values</a>(
|
|
clEnumVal(dce , "<i>Dead Code Elimination</i>"),
|
|
clEnumVal(constprop , "<i>Constant Propagation</i>"),
|
|
clEnumValN(inlining, "<i>inline</i>", "<i>Procedure Integration</i>"),
|
|
clEnumVal(strip , "<i>Strip Symbols</i>"),
|
|
0));
|
|
</pre><p>
|
|
|
|
This defines a variable that is conceptually of the type
|
|
"<tt>std::vector<enum Opts></tt>". Thus, you can access it with standard
|
|
vector methods:<p>
|
|
|
|
<pre>
|
|
for (unsigned i = 0; i != OptimizationList.size(); ++i)
|
|
switch (OptimizationList[i])
|
|
...
|
|
</pre>
|
|
|
|
... to iterate through the list of options specified.<p>
|
|
|
|
Note that the "<tt><a href="#cl::list">cl::list</a></tt>" template is completely general and may be used
|
|
with any data types or other arguments that you can use with the
|
|
"<tt><a href="#cl::opt">cl::opt</a></tt>" template. One especially useful way to use a list is to
|
|
capture all of the positional arguments together if there may be more than one
|
|
specified. In the case of a linker, for example, the linker takes several
|
|
'<tt>.o</tt>' files, and needs to capture them into a list. This is naturally
|
|
specified as:<p>
|
|
|
|
<pre>
|
|
...
|
|
<a href="#cl::list">cl::list</a><std::string> InputFilenames(<a href="#cl::Positional">cl::Positional</a>, <a href="#cl::desc">cl::desc</a>("<Input files>"), <a href="#cl::OneOrMore">cl::OneOrMore</a>);
|
|
...
|
|
</pre><p>
|
|
|
|
This variable works just like a "<tt>vector<string></tt>" object. As
|
|
such, accessing the list is simple, just like above. In this example, we used
|
|
the <tt><a href="#cl::OneOrMore">cl::OneOrMore</a></tt> modifier to inform the
|
|
CommandLine library that it is an error if the user does not specify any
|
|
<tt>.o</tt> files on our command line. Again, this just reduces the amount of
|
|
checking we have to do.<p>
|
|
|
|
|
|
|
|
<!-- ======================================================================= -->
|
|
</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0><tr><td> </td><td width="100%"> <font color="#EEEEFF" face="Georgia,Palatino"><b>
|
|
<a name="description">Adding freeform text to help output
|
|
</b></font></td></tr></table><ul>
|
|
|
|
As our program grows and becomes more mature, we may decide to put summary
|
|
information about what it does into the help output. The help output is styled
|
|
to look similar to a Unix <tt>man</tt> page, providing concise information about
|
|
a program. Unix <tt>man</tt> pages, however often have a description about what
|
|
the program does. To add this to your CommandLine program, simply pass a third
|
|
argument to the <a
|
|
href="#cl::ParseCommandLineOptions"><tt>cl::ParseCommandLineOptions</tt></a>
|
|
call in main. This additional argument is then printed as the overview
|
|
information for your program, allowing you to include any additional information
|
|
that you want. For example:<p>
|
|
|
|
<pre>
|
|
int main(int argc, char **argv) {
|
|
<a href="#cl::ParseCommandLineOptions">cl::ParseCommandLineOptions</a>(argc, argv, " CommandLine compiler example\n\n"
|
|
" This program blah blah blah...\n");
|
|
...
|
|
}
|
|
</pre><p>
|
|
|
|
Would yield the help output:
|
|
|
|
<pre>
|
|
<b>OVERVIEW: CommandLine compiler example
|
|
|
|
This program blah blah blah...</b>
|
|
|
|
USAGE: compiler [options] <input file>
|
|
|
|
OPTIONS:
|
|
...
|
|
-help - display available options (--help-hidden for more)
|
|
-o <filename> - Specify output filename
|
|
</pre><p>
|
|
|
|
|
|
|
|
|
|
<!-- *********************************************************************** -->
|
|
</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0><tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
|
|
<a name="referenceguide">Reference Guide
|
|
</b></font></td></tr></table><ul>
|
|
<!-- *********************************************************************** -->
|
|
|
|
Now that you know the basics of how to use the CommandLine library, this section
|
|
will give you the detailed information you need to tune how command line options
|
|
work, as well as information on more "advanced" command line option processing
|
|
capabilities.<p>
|
|
|
|
|
|
<!-- ======================================================================= -->
|
|
</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0><tr><td> </td><td width="100%"> <font color="#EEEEFF" face="Georgia,Palatino"><b>
|
|
<a name="positional">Positional Arguments
|
|
</b></font></td></tr></table><ul>
|
|
|
|
Positional arguments are those arguments that are not named, and are not
|
|
specified with a hyphen. Positional arguments should be used when an option is
|
|
specified by its position alone. For example, the standard Unix <tt>grep</tt>
|
|
tool takes a regular expression argument, and an optional filename to search
|
|
through (which defaults to standard input if a filename is not specified).
|
|
Using the CommandLine library, this would be specified as:<p>
|
|
|
|
<pre>
|
|
<a href="#cl::opt">cl::opt</a><string> Regex (<a href="#cl::Positional">cl::Positional</a>, <a href="#cl::desc">cl::desc</a>("<i><regular expression></i>"), <a href="#cl::Required">cl::Required</a>);
|
|
<a href="#cl::opt">cl::opt</a><string> Filename(<a href="#cl::Positional">cl::Positional</a>, <a href="#cl::desc">cl::desc</a>("<i><input file></i>"), <a href="#cl::init">cl::init</a>("<i>-</i>"));
|
|
</pre>
|
|
|
|
Given these two option declarations, the <tt>--help</tt> output for our grep
|
|
replacement would look like this:<p>
|
|
|
|
<pre>
|
|
USAGE: spiffygrep [options] <b><regular expression> <input file></b>
|
|
|
|
OPTIONS:
|
|
-help - display available options (--help-hidden for more)
|
|
</pre>
|
|
|
|
... and the resultant program could be used just like the standard <tt>grep</tt>
|
|
tool.<p>
|
|
|
|
Positional arguments are sorted by their order of construction. This means that
|
|
command line options will be ordered according to how they are listed in a .cpp
|
|
file, but will not have an ordering defined if they positional arguments are
|
|
defined in multiple .cpp files. The fix for this problem is simply to define
|
|
all of your positional arguments in one .cpp file.<p>
|
|
|
|
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
</ul><a name="--"><h4><hr size=0>Specifying positional options with hyphens</h4><ul>
|
|
|
|
Sometimes you may want to specify a value to your positional argument that
|
|
starts with a hyphen (for example, searching for '<tt>-foo</tt>' in a file). At
|
|
first, you will have trouble doing this, because it will try to find an argument
|
|
named '<tt>-foo</tt>', and will fail (and single quotes will not save you).
|
|
Note that the system <tt>grep</tt> has the same problem:<p>
|
|
|
|
<pre>
|
|
$ spiffygrep '-foo' test.txt
|
|
Unknown command line argument '-foo'. Try: spiffygrep --help'
|
|
|
|
$ grep '-foo' test.txt
|
|
grep: illegal option -- f
|
|
grep: illegal option -- o
|
|
grep: illegal option -- o
|
|
Usage: grep -hblcnsviw pattern file . . .
|
|
</pre><p>
|
|
|
|
The solution for this problem is the same for both your tool and the system
|
|
version: use the '<tt>--</tt>' marker. When the user specifies '<tt>--</tt>' on
|
|
the command line, it is telling the program that all options after the
|
|
'<tt>--</tt>' should be treated as positional arguments, not options. Thus, we
|
|
can use it like this:<p>
|
|
|
|
<pre>
|
|
$ spiffygrep -- -foo test.txt
|
|
...output...
|
|
</pre><p>
|
|
|
|
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
</ul><a name="cl::ConsumeAfter"><h4><hr size=0>The <tt>cl::ConsumeAfter</tt> modifier</h4><ul>
|
|
|
|
The <tt>cl::ConsumeAfter</tt> <a href="#formatting">formatting option</a> is
|
|
used to construct programs that use "interpreter style" option processing. With
|
|
this style of option processing, all arguments specified after the last
|
|
positional argument are treated as special interpreter arguments that are not
|
|
interpreted by the command line argument.<p>
|
|
|
|
As a concrete example, lets say we are developing a replacement for the standard
|
|
Unix Bourne shell (<tt>/bin/sh</tt>). To run <tt>/bin/sh</tt>, first you
|
|
specify options to the shell itself (like <tt>-x</tt> which turns on trace
|
|
output), then you specify the name of the script to run, then you specify
|
|
arguments to the script. These arguments to the script are parsed by the bourne
|
|
shell command line option processor, but are not interpreted as options to the
|
|
shell itself. Using the CommandLine library, we would specify this as:<p>
|
|
|
|
<pre>
|
|
<a href="#cl::opt">cl::opt</a><string> Script(<a href="#cl::Positional">cl::Positional</a>, <a href="#cl::desc">cl::desc</a>("<i><input script></i>"), <a href="#cl::init">cl::init</a>("-"));
|
|
<a href="#cl::list">cl::list</a><string> Argv(<a href="#cl::ConsumeAfter">cl::ConsumeAfter</a>, <a href="#cl::desc">cl::desc</a>("<i><program arguments>...</i>"));
|
|
<a href="#cl::opt">cl::opt</a><bool> Trace("<i>x</i>", <a href="#cl::desc">cl::desc</a>("<i>Enable trace output</i>"));
|
|
</pre><p>
|
|
|
|
which automatically provides the help output:<p>
|
|
|
|
<pre>
|
|
USAGE: spiffysh [options] <b><input script> <program arguments>...</b>
|
|
|
|
OPTIONS:
|
|
-help - display available options (--help-hidden for more)
|
|
<b>-x - Enable trace output</b>
|
|
</pre><p>
|
|
|
|
At runtime, if we run our new shell replacement as '<tt>spiffysh -x test.sh -a
|
|
-x -y bar</tt>', the <tt>Trace</tt> variable will be set to true, the
|
|
<tt>Script</tt> variable will be set to "<tt>test.sh</tt>", and the
|
|
<tt>Argv</tt> list will contain <tt>["-a", "-x", "-y", "bar"]</tt>, because
|
|
they were specified after the last positional argument (which is the script
|
|
name).<p>
|
|
|
|
There are several limitations to when <tt>cl::ConsumeAfter</tt> options can be
|
|
specified. For example, only one <tt>cl::ConsumeAfter</tt> can be specified per
|
|
program, there must be at least one <a href="#positional">positional
|
|
argument</a> specified, and the <tt>cl::ConsumeAfter</tt> option should be a <a
|
|
href="#cl::list">cl::list</a> option.<p>
|
|
|
|
|
|
|
|
<!-- ======================================================================= -->
|
|
</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0><tr><td> </td><td width="100%"> <font color="#EEEEFF" face="Georgia,Palatino"><b>
|
|
<a name="storage">Internal vs External Storage
|
|
</b></font></td></tr></table><ul>
|
|
|
|
By default, all command line options automatically hold the value that they
|
|
parse from the command line. This is very convenient in the common case,
|
|
especially when combined with the ability to define command line options in the
|
|
files that use them. This is called the internal storage model.<p>
|
|
|
|
Sometimes, however, it is nice to separate the command line option processing
|
|
code from the storage of the value parsed. For example, lets say that we have a
|
|
'<tt>-debug</tt>' option that we would like to use to enable debug information
|
|
across the entire body of our program. In this case, the boolean value
|
|
controlling the debug code should be globally accessable (in a header file, for
|
|
example) yet the command line option processing code should not be exposed to
|
|
all of these clients (requiring lots of .cpp files to #include
|
|
<tt>CommandLine.h</tt>).<p>
|
|
|
|
To do this, set up your .h file with your option, like this for example:<p>
|
|
|
|
<pre>
|
|
<i>// DebugFlag.h - Get access to the '-debug' command line option
|
|
//
|
|
|
|
// DebugFlag - This boolean is set to true if the '-debug' command line option
|
|
// is specified. This should probably not be referenced directly, instead, use
|
|
// the DEBUG macro below.
|
|
//</i>
|
|
extern bool DebugFlag;
|
|
|
|
<i>// DEBUG macro - This macro should be used by code to emit debug information.
|
|
// In the '-debug' option is specified on the command line, and if this is a
|
|
// debug build, then the code specified as the option to the macro will be
|
|
// executed. Otherwise it will not be. Example:
|
|
//
|
|
// DEBUG(cerr << "Bitset contains: " << Bitset << "\n");
|
|
//</i>
|
|
<font color=red>#ifdef NDEBUG
|
|
#define DEBUG(X)
|
|
#else
|
|
#define DEBUG(X)</font> \
|
|
do { if (DebugFlag) { X; } } while (0)
|
|
<font color=red>#endif</font>
|
|
</pre>
|
|
|
|
This allows clients to blissfully use the <tt>DEBUG()</tt> macro, or the
|
|
<tt>DebugFlag</tt> explicitly if they want to. Now we just need to be able to
|
|
set the <tt>DebugFlag</tt> boolean when the option is set. To do this, we pass
|
|
an additial argument to our command line argument processor, and we specify
|
|
where to fill in with the <a href="#cl::location">cl::location</a> attribute:<p>
|
|
|
|
<pre>
|
|
bool DebugFlag; <i>// the actual value</i>
|
|
static <a href="#cl::opt">cl::opt</a><bool, true> <i>// The parser</i>
|
|
Debug("<i>debug</i>", <a href="#cl::desc">cl::desc</a>("<i>Enable debug output</i>")</a>, <a href="#cl::Hidden">cl::Hidden</a>,
|
|
<a href="#cl::location">cl::location</a>(DebugFlag));
|
|
</pre>
|
|
|
|
In the above example, we specify "<tt>true</tt>" as the second argument to the
|
|
<a href="#cl::opt">cl::opt</a> template, indicating that the template should not
|
|
maintain a copy of the value itself. In addition to this, we specify the <a
|
|
href="#cl::location">cl::location</a> attribute, so that <tt>DebugFlag</tt> is
|
|
automatically set.<p>
|
|
|
|
|
|
|
|
<!-- ======================================================================= -->
|
|
</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0><tr><td> </td><td width="100%"> <font color="#EEEEFF" face="Georgia,Palatino"><b>
|
|
<a name="attributes">Option Attributes
|
|
</b></font></td></tr></table><ul>
|
|
|
|
This section describes the basic attributes that you can specify on options.<p>
|
|
|
|
<ul>
|
|
|
|
<li>The option name attribute (which is required for all options, except <a
|
|
href="#positional">positional options</a>) specifies what the option name is.
|
|
This option is specified in simple double quotes:<p>
|
|
|
|
<pre>
|
|
<a href="#cl::opt">cl::opt</a><<b>bool</b>> Quiet("<i>quiet</i>");
|
|
</pre><p>
|
|
|
|
<li><a name="cl::desc">The <b><tt>cl::desc</tt></b> attribute specifies a
|
|
description for the option to be shown in the <tt>--help</tt> output for the
|
|
program.<p>
|
|
|
|
<li><a name="cl::value_desc">The <b><tt>cl::value_desc</tt></b> attribute
|
|
specifies a string that can be used to fine tune the <tt>--help</tt> output for
|
|
a command line option. Look <a href="#value_desc_example">here</a> for an
|
|
example.<p>
|
|
|
|
<li><a name="cl::init">The <b><tt>cl::init</tt></b> attribute specifies an
|
|
inital value for a <a href="#cl::opt">scalar</a> option. If this attribute is
|
|
not specified then the command line option value defaults to the value created
|
|
by the default constructor for the type. <b>Warning</b>: If you specify both
|
|
<b><tt>cl::init</tt></b> and <b><tt>cl::location</tt></b> for an option,
|
|
you must specify <b><tt>cl::location</tt></b> first, so that when the
|
|
command-line parser sees <b><tt>cl::init</tt></b>, it knows where to put the
|
|
initial value. (You will get an error at runtime if you don't put them in
|
|
the right order.)<p>
|
|
|
|
<li><a name="cl::location">The <b><tt>cl::location</tt></b> attribute where to
|
|
store the value for a parsed command line option if using external storage. See
|
|
the section on <a href="#storage">Internal vs External Storage</a> for more
|
|
information.<p>
|
|
|
|
<li><a name="cl::aliasopt">The <b><tt>cl::aliasopt</tt></b> attribute specifies
|
|
which option a <a href="#cl::alias">cl::alias</a> option is an alias for.<p>
|
|
|
|
<li><a name="cl::values">The <b><tt>cl::values</tt></b> attribute specifies the
|
|
string-to-value mapping to be used by the generic parser. It takes a <b>null
|
|
terminated</b> list of (option, value, description) triplets that specify the
|
|
option name, the value mapped to, and the description shown in the
|
|
<tt>--help</tt> for the tool. Because the generic parser is used most frequently with enum values, two macros are often useful:<p>
|
|
<ol>
|
|
<li><a name="clEnumVal">The <b><tt>clEnumVal</tt></b> macro is used as a nice
|
|
simple way to specify a triplet for an enum. This macro automatically makes the
|
|
option name be the same as the enum name. The first option to the macro is the
|
|
enum, the second is the description for the command line option.<p> <li><a
|
|
name="clEnumValN">The <b><tt>clEnumValN</tt></b> macro is used to specify macro
|
|
options where the option name doesn't equal the enum name. For this macro, the
|
|
first argument is the enum value, the second is the flag name, and the second is
|
|
the description.<p>
|
|
</ol>
|
|
|
|
You will get a compile time error if you try to use cl::values with a parser
|
|
that does not support it.<p>
|
|
|
|
</ul>
|
|
|
|
|
|
|
|
<!-- ======================================================================= -->
|
|
</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0><tr><td> </td><td width="100%"> <font color="#EEEEFF" face="Georgia,Palatino"><b>
|
|
<a name="modifiers">Option Modifiers
|
|
</b></font></td></tr></table><ul>
|
|
|
|
Option modifiers are the flags and expressions that you pass into the
|
|
constructors for <tt><a href="#cl::opt">cl::opt</a></tt> and <tt><a
|
|
href="#cl::list">cl::list</a></tt>. These modifiers give you the ability to
|
|
tweak how options are parsed and how <tt>--help</tt> output is generated to fit
|
|
your application well.<p>
|
|
|
|
These options fall into five main catagories:<p>
|
|
|
|
<ol>
|
|
<li><a href="#hiding">Hiding an option from <tt>--help</tt> output</a>
|
|
<li><a href="#numoccurances">Controlling the number of occurances
|
|
required and allowed</a>
|
|
<li><a href="#valrequired">Controlling whether or not a value must be
|
|
specified</a>
|
|
<li><a href="#formatting">Controlling other formatting options</a>
|
|
<li><a href="#misc">Miscellaneous option modifiers</a>
|
|
</ol><p>
|
|
|
|
It is not possible to specify two options from the same catagory (you'll get a
|
|
runtime error) to a single option, except for options in the miscellaneous
|
|
catagory. The CommandLine library specifies defaults for all of these settings
|
|
that are the most useful in practice and the most common, which mean that you
|
|
usually shouldn't have to worry about these.<p>
|
|
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
</ul><a name="hiding"><h4><hr size=0>Hiding an option from <tt>--help</tt> output</h4><ul>
|
|
|
|
The <tt>cl::NotHidden</tt>, <tt>cl::Hidden</tt>, and <tt>cl::ReallyHidden</tt>
|
|
modifiers are used to control whether or not an option appears in the
|
|
<tt>--help</tt> and <tt>--help-hidden</tt> output for the compiled program:<p>
|
|
|
|
<ul>
|
|
|
|
<a name="cl::NotHidden">The <b><tt>cl::NotHidden</tt></b> modifier (which is the
|
|
default for <tt><a href="#cl::opt">cl::opt</a></tt> and <tt><a
|
|
href="#cl::list">cl::list</a></tt> options), indicates the option is to appear
|
|
in both help listings.<p>
|
|
|
|
<a name="cl::Hidden">The <b><tt>cl::Hidden</tt></b> modifier (which is the
|
|
default for <tt><a href="#cl::alias">cl::alias</a></tt> options), indicates that
|
|
the option should not appear in the <tt>--help</tt> output, but should appear in
|
|
the <tt>--help-hidden</tt> output.<p>
|
|
|
|
<a name="cl::ReallyHidden">The <b><tt>cl::ReallyHidden</tt></b> modifier,
|
|
indicates that the option should not appear in any help output.<p>
|
|
</ul>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
</ul><a name="numoccurances"><h4><hr size=0>Controlling the number of occurances required and allowed</h4><ul>
|
|
|
|
This group of options is used to control how many time an option is allowed (or
|
|
required) to be specified on the command line of your program. Specifying a
|
|
value for this setting allows the CommandLine library to do error checking for
|
|
you.<p>
|
|
|
|
The allowed values for this option group are:<p>
|
|
|
|
<ul>
|
|
<a name="cl::Optional">The <b><tt>cl::Optional</tt></b> modifier (which is the
|
|
default for the <tt><a href="#cl::opt">cl::opt</a></tt> and <tt><a
|
|
href="#cl::alias">cl::alias</a></tt> classes) indicates that your program will
|
|
allow either zero or one occurance of the option to be specified.<p>
|
|
|
|
<a name="cl::ZeroOrMore">The <b><tt>cl::ZeroOrMore</tt></b> modifier (which is
|
|
the default for the <tt><a href="#cl::list">cl::list</a></tt> class) indicates
|
|
that your program will allow the option to be specified zero or more times.<p>
|
|
|
|
<a name="cl::Required">The <b><tt>cl::Required</tt></b> modifier indicates that
|
|
the specified option must be specified exactly one time.<p>
|
|
|
|
<a name="cl::OneOrMore">The <b><tt>cl::OneOrMore</tt></b> modifier indicates
|
|
that the option must be specified at least one time.<p>
|
|
|
|
The <b><tt>cl::ConsumeAfter</tt></b> modifier is described in the <a
|
|
href="#positional">Positional arguments section</a><p>
|
|
|
|
</ul>
|
|
|
|
If an option is not specified, then the value of the option is equal to the
|
|
value specified by the <tt><a href="#cl::init">cl::init</a></tt> attribute. If
|
|
the <tt><a href="#cl::init">cl::init</a></tt> attribute is not specified, the
|
|
option value is initialized with the default constructor for the data type.<p>
|
|
|
|
If an option is specified multiple times for an option of the <tt><a
|
|
href="#cl::opt">cl::opt</a></tt> class, only the last value will be retained.<p>
|
|
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
</ul><a name="valrequired"><h4><hr size=0>Controlling whether or not a value must be specified</h4><ul>
|
|
|
|
This group of options is used to control whether or not the option allows a
|
|
value to be present. In the case of the CommandLine library, a value is either
|
|
specified with an equal sign (e.g. '<tt>-index-depth=17</tt>') or as a trailing
|
|
string (e.g. '<tt>-o a.out</tt>').<p>
|
|
|
|
The allowed values for this option group are:<p>
|
|
|
|
<ul>
|
|
<a name="cl::ValueOptional">The <b><tt>cl::ValueOptional</tt></b> modifier
|
|
(which is the default for <tt>bool</tt> typed options) specifies that it is
|
|
acceptable to have a value, or not. A boolean argument can be enabled just by
|
|
appearing on the command line, or it can have an explicit '<tt>-foo=true</tt>'.
|
|
If an option is specified with this mode, it is illegal for the value to be
|
|
provided without the equal sign. Therefore '<tt>-foo true</tt>' is illegal. To
|
|
get this behavior, you must use the <a
|
|
href="#cl::ValueRequired">cl::ValueRequired</a> modifier.<p>
|
|
|
|
<a name="cl::ValueRequired">The <b><tt>cl::ValueRequired</tt></b> modifier
|
|
(which is the default for all other types except for <a
|
|
href="#onealternative">unnamed alternatives using the generic parser</a>)
|
|
specifies that a value must be provided. This mode informs the command line
|
|
library that if an option is not provides with an equal sign, that the next
|
|
argument provided must be the value. This allows things like '<tt>-o
|
|
a.out</tt>' to work.<p>
|
|
|
|
<a name="cl::ValueDisallowed">The <b><tt>cl::ValueDisallowed</tt></b> modifier
|
|
(which is the default for <a href="#onealternative">unnamed alternatives using
|
|
the generic parser</a>) indicates that it is a runtime error for the user to specify a value. This can be provided to disallow users from providing options to boolean options (like '<tt>-foo=true</tt>').<p>
|
|
|
|
</ul>
|
|
|
|
In general, the default values for this option group work just like you would
|
|
want them to. As mentioned above, you can specify the <a
|
|
href="#cl::ValueDisallowed">cl::ValueDisallowed</a> modifier to a boolean
|
|
argument to restrict your command line parser. These options are mostly useful
|
|
when <a href="#extensionguide">extending the library</a>.<p>
|
|
|
|
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
</ul><a name="formatting"><h4><hr size=0>Controlling other formatting options</h4><ul>
|
|
|
|
The formatting option group is used to specify that the command line option has
|
|
special abilities and is otherwise different from other command line arguments.
|
|
As usual, you can only specify at most one of these arguments.<p>
|
|
|
|
<ul>
|
|
<a name="cl::NormalFormatting">The <b><tt>cl::NormalFormatting</tt></b> modifier
|
|
(which is the default all options) specifies that this option is "normal".<p>
|
|
|
|
<a name="cl::Positional">The <b><tt>cl::Positional</tt></b> modifier specifies
|
|
that this is a positional argument, that does not have a command line option
|
|
associated with it. See the <a href="#positional">Positional Arguments</a>
|
|
section for more information.<p>
|
|
|
|
The <b><a href="#cl::ConsumeAfter"><tt>cl::ConsumeAfter</tt></a></b> modifier
|
|
specifies that this option is used to capture "interpreter style" arguments. See <a href="#cl::ConsumeAfter">this section for more information</a>.<p>
|
|
|
|
|
|
<a name="cl::Prefix">The <b><tt>cl::Prefix</tt></b> modifier specifies that this
|
|
option prefixes its value. With 'Prefix' options, there is no equal sign that
|
|
separates the value from the option name specified. This is useful for
|
|
processing odd arguments like '<tt>-lmalloc -L/usr/lib'</tt> in a linker tool.
|
|
Here, the '<tt>l</tt>' and '<tt>L</tt>' options are normal string (list)
|
|
options, that have the <a href="#cl::Prefix">cl::Prefix</a> modifier added to
|
|
allow the CommandLine library to recognize them. Note that <a
|
|
href="#cl::Prefix">cl::Prefix</a> options must not have the <a
|
|
href="#cl::ValueDisallowed">cl::ValueDisallowed</a> modifier specified.<p>
|
|
|
|
<a name="cl::Grouping">The <b><tt>cl::Grouping</tt></b> modifier is used to
|
|
implement unix style tools (like <tt>ls</tt>) that have lots of single letter
|
|
arguments, but only require a single dash. For example, the '<tt>ls -labF</tt>'
|
|
command actually enables four different options, all of which are single
|
|
letters. Note that <a href="#cl::Grouping">cl::Grouping</a> options cannot have
|
|
values.<p>
|
|
|
|
</ul>
|
|
|
|
The CommandLine library does not restrict how you use the <a
|
|
href="#cl::Prefix">cl::Prefix</a> or <a href="#cl::Grouping">cl::Grouping</a>
|
|
modifiers, but it is possible to specify ambiguous argument settings. Thus, it
|
|
is possible to have multiple letter options that are prefix or grouping options,
|
|
and they will still work as designed.<p>
|
|
|
|
To do this, the CommandLine library uses a greedy algorithm to parse the input
|
|
option into (potentially multiple) prefix and grouping options. The strategy
|
|
basically looks like this:<p>
|
|
|
|
<tt>parse(string OrigInput) {</tt>
|
|
<ol>
|
|
<li><tt>string input = OrigInput;</tt>
|
|
<li><tt>if (isOption(input)) return getOption(input).parse();</tt> <i>// Normal option</i>
|
|
<li><tt>while (!isOption(input) && !input.empty()) input.pop_back();</tt> <i>// Remove the last letter</i>
|
|
<li><tt>if (input.empty()) return error();</tt> <i>// No matching option</i>
|
|
<li><tt>if (getOption(input).isPrefix())<br>
|
|
return getOption(input).parse(input);</tt>
|
|
<li><tt>while (!input.empty()) { <i>// Must be grouping options</i><br>
|
|
getOption(input).parse();<br>
|
|
OrigInput.erase(OrigInput.begin(), OrigInput.begin()+input.length());<br>
|
|
input = OrigInput;<br>
|
|
while (!isOption(input) && !input.empty()) input.pop_back();<br>
|
|
}</tt>
|
|
<li><tt>if (!OrigInput.empty()) error();</tt>
|
|
</tt>
|
|
|
|
</ol>
|
|
<tt>}</tt><p>
|
|
|
|
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
</ul><a name="misc"><h4><hr size=0>Miscellaneous option modifiers</h4><ul>
|
|
|
|
The miscellaneous option modifiers are the only flags where you can specify more
|
|
than one flag from the set: they are not mutually exclusive. These flags
|
|
specify boolean properties that modify the option.<p>
|
|
|
|
<ul>
|
|
|
|
<a name="cl::CommaSeparated">The <b><tt>cl::CommaSeparated</tt></b> modifier
|
|
indicates that any commas specified for an option's value should be used to
|
|
split the value up into multiple values for the option. For example, these two
|
|
options are equivalent when <tt>cl::CommaSeparated</tt> is specified:
|
|
"<tt>-foo=a -foo=b -foo=c</tt>" and "<tt>-foo=a,b,c</tt>". This option only
|
|
makes sense to be used in a case where the option is allowed to accept one or
|
|
more values (i.e. it is a <a href="#cl::list">cl::list</a> option).<p>
|
|
</ul>
|
|
|
|
So far, the only miscellaneous option modifier is the
|
|
<tt>cl::CommaSeparated</tt> modifier.<p>
|
|
|
|
|
|
<!-- ======================================================================= -->
|
|
</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0><tr><td> </td><td width="100%"> <font color="#EEEEFF" face="Georgia,Palatino"><b>
|
|
<a name="toplevel">Top-Level Classes and Functions
|
|
</b></font></td></tr></table><ul>
|
|
|
|
Despite all of the builtin flexibility, the CommandLine option library really
|
|
only consists of one function (<a
|
|
href="#cl::ParseCommandLineOptions"><tt>cl::ParseCommandLineOptions</tt></a>)
|
|
and three main classes: <a href="#cl::opt"><tt>cl::opt</tt></a>, <a
|
|
href="#cl::list"><tt>cl::list</tt></a>, and <a
|
|
href="#cl::alias"><tt>cl::alias</tt></a>. This section describes these three
|
|
classes in detail.<p>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
</ul><a name="cl::ParseCommandLineOptions"><h4><hr size=0>The
|
|
<tt>cl::ParseCommandLineOptions</tt> function</h4><ul>
|
|
|
|
The <tt>cl::ParseCommandLineOptions</tt> function is designed to be called
|
|
directly from <tt>main</tt>, and is used to fill in the values of all of the
|
|
command line option variables once <tt>argc</tt> and <tt>argv</tt> are
|
|
available.<p>
|
|
|
|
The <tt>cl::ParseCommandLineOptions</tt> function requires two parameters
|
|
(<tt>argc</tt> and <tt>argv</tt>), but may also take an optional third parameter
|
|
which holds <a href="#description">additional extra text</a> to emit when the
|
|
<tt>--help</tt> option is invoked.<p>
|
|
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
</ul><a name="cl::ParseEnvironmentOptions"><h4><hr size=0>The
|
|
<tt>cl::ParseEnvironmentOptions</tt> function</h4><ul>
|
|
|
|
The <tt>cl::ParseEnvironmentOptions</tt>
|
|
function has mostly the same effects as
|
|
<a href="#cl::ParseCommandLineOptions"><tt>cl::ParseCommandLineOptions</tt></a>,
|
|
except that it is designed to take values for options from an
|
|
environment variable, for those cases in which reading the
|
|
command line is not convenient or not desired. It fills in
|
|
the values of all the command line option variables just like
|
|
<a href="#cl::ParseCommandLineOptions"><tt>cl::ParseCommandLineOptions</tt></a>
|
|
does.<p>
|
|
|
|
It takes three parameters: first, the name of the program (since <tt>argv</tt>
|
|
may not be available, it can't just look in <tt>argv[0]</tt>), second,
|
|
the name of the environment variable to examine, and third, the optional
|
|
<a href="#description">additional extra text</a> to emit when the
|
|
<tt>--help</tt> option is invoked.<p>
|
|
|
|
<tt>cl::ParseEnvironmentOptions</tt> will break the environment
|
|
variable's value up into words and then process them using
|
|
<a href="#cl::ParseCommandLineOptions"><tt>cl::ParseCommandLineOptions</tt></a>.
|
|
<b>Note:</b> Currently <tt>cl::ParseEnvironmentOptions</tt> does not support
|
|
quoting, so an environment variable containing <tt>-option "foo bar"</tt> will
|
|
be parsed as three words, <tt>-option</tt>, <tt>"foo</tt>, and <tt>bar"</tt>,
|
|
which is different from what you would get from the shell with the same
|
|
input.<p>
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
</ul><a name="cl::opt"><h4><hr size=0>The <tt>cl::opt</tt> class</h4><ul>
|
|
|
|
The <tt>cl::opt</tt> class is the class used to represent scalar command line
|
|
options, and is the one used most of the time. It is a templated class which
|
|
can take up to three arguments (all except for the first have default values
|
|
though):<p>
|
|
|
|
<pre>
|
|
<b>namespace</b> cl {
|
|
<b>template</b> <<b>class</b> DataType, <b>bool</b> ExternalStorage = <b>false</b>,
|
|
<b>class</b> ParserClass = parser<DataType> >
|
|
<b>class</b> opt;
|
|
}
|
|
</pre><p>
|
|
|
|
The first template argument specifies what underlying data type the command line
|
|
argument is, and is used to select a default parser implementation. The second
|
|
template argument is used to specify whether the option should contain the
|
|
storage for the option (the default) or whether external storage should be used
|
|
to contain the value parsed for the option (see <a href="#storage">Internal vs
|
|
External Storage</a> for more information).<p>
|
|
|
|
The third template argument specifies which parser to use. The default value
|
|
selects an instantiation of the <tt>parser</tt> class based on the underlying
|
|
data type of the option. In general, this default works well for most
|
|
applications, so this option is only used when using a <a
|
|
href="#customparser">custom parser</a>.<p>
|
|
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
</ul><a name="cl::list"><h4><hr size=0>The <tt>cl::list</tt> class</h4><ul>
|
|
|
|
The <tt>cl::list</tt> class is the class used to represent a list of command
|
|
line options. It too is a templated class which can take up to three
|
|
arguments:<p>
|
|
|
|
<pre>
|
|
<b>namespace</b> cl {
|
|
<b>template</b> <<b>class</b> DataType, <b>class</b> Storage = <b>bool</b>,
|
|
<b>class</b> ParserClass = parser<DataType> >
|
|
<b>class</b> list;
|
|
}
|
|
</pre><p>
|
|
|
|
This class works the exact same as the <a href="#cl::opt"><tt>cl::opt</tt></a>
|
|
class, except that the second argument is the <b>type</b> of the external
|
|
storage, not a boolean value. For this class, the marker type '<tt>bool</tt>'
|
|
is used to indicate that internal storage should be used.<p>
|
|
|
|
|
|
<!-- _______________________________________________________________________ -->
|
|
</ul><a name="cl::alias"><h4><hr size=0>The <tt>cl::alias</tt> class</h4><ul>
|
|
|
|
The <tt>cl::alias</tt> class is a nontemplated class that is used to form
|
|
aliases for other arguments.<p>
|
|
|
|
<pre>
|
|
<b>namespace</b> cl {
|
|
<b>class</b> alias;
|
|
}
|
|
</pre></p>
|
|
|
|
The <a href="#cl::aliasopt"><tt>cl::aliasopt</tt></a> attribute should be used
|
|
to specify which option this is an alias for. Alias arguments default to being
|
|
<a href="#cl::Hidden">Hidden</a>, and use the aliased options parser to do the
|
|
conversion from string to data.<p>
|
|
|
|
|
|
<!-- ======================================================================= -->
|
|
</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0><tr><td> </td><td width="100%"> <font color="#EEEEFF" face="Georgia,Palatino"><b>
|
|
<a name="builtinparsers">Builtin parsers
|
|
</b></font></td></tr></table><ul>
|
|
|
|
Parsers control how the string value taken from the command line is translated
|
|
into a typed value, suitable for use in a C++ program. By default, the
|
|
CommandLine library uses an instance of <tt>parser<type></tt> if the
|
|
command line option specifies that it uses values of type '<tt>type</tt>'.
|
|
Because of this, custom option processing is specified with specializations of
|
|
the '<tt>parser</tt>' class.<p>
|
|
|
|
The CommandLine library provides the following builtin parser specializations,
|
|
which are sufficient for most applications. It can, however, also be extended to
|
|
work with new data types and new ways of interpreting the same data. See the <a
|
|
href="#customparser">Writing a Custom Parser</a> for more details on this type
|
|
of library extension.<p>
|
|
|
|
<li><a name="genericparser">The <b>generic <tt>parser<t></tt> parser</b>
|
|
can be used to map strings values to any data type, through the use of the <a
|
|
href="#cl::values">cl::values</a> property, which specifies the mapping
|
|
information. The most common use of this parser is for parsing enum values,
|
|
which allows you to use the CommandLine library for all of the error checking to
|
|
make sure that only valid enum values are specified (as opposed to accepting
|
|
arbitrary strings). Despite this, however, the generic parser class can be used
|
|
for any data type.<p>
|
|
|
|
<li><a name="boolparser">The <b><tt>parser<bool></tt> specialization</b>
|
|
is used to convert boolean strings to a boolean value. Currently accepted
|
|
strings are "<tt>true</tt>", "<tt>TRUE</tt>", "<tt>True</tt>", "<tt>1</tt>",
|
|
"<tt>false</tt>", "<tt>FALSE</tt>", "<tt>False</tt>", and "<tt>0</tt>".<p>
|
|
|
|
<li><a name="stringparser">The <b><tt>parser<string></tt> specialization</b> simply stores the parsed string into the string value specified. No conversion or modification of the data is performed.<p>
|
|
|
|
<li><a name="intparser">The <b><tt>parser<int></tt> specialization</b>
|
|
uses the C <tt>strtol</tt> function to parse the string input. As such, it will
|
|
accept a decimal number (with an optional '+' or '-' prefix) which must start
|
|
with a non-zero digit. It accepts octal numbers, which are identified with a
|
|
'<tt>0</tt>' prefix digit, and hexadecimal numbers with a prefix of
|
|
'<tt>0x</tt>' or '<tt>0X</tt>'.<p>
|
|
|
|
<li><a name="doubleparser">The <b><tt>parser<double></tt></b> and
|
|
<b><tt>parser<float></tt> specializations</b> use the standard C
|
|
<tt>strtod</tt> function to convert floating point strings into floating point
|
|
values. As such, a broad range of string formats is supported, including
|
|
exponential notation (ex: <tt>1.7e15</tt>) and properly supports locales.
|
|
<p>
|
|
|
|
|
|
|
|
<!-- *********************************************************************** -->
|
|
</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0><tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
|
|
<a name="extensionguide">Extension Guide
|
|
</b></font></td></tr></table><ul>
|
|
<!-- *********************************************************************** -->
|
|
|
|
Although the CommandLine library has a lot of functionality built into it
|
|
already (as discussed previously), one of its true strengths lie in its
|
|
extensibility. This section discusses how the CommandLine library works under
|
|
the covers and illustrates how to do some simple, common, extensions.<p>
|
|
|
|
|
|
<!-- ======================================================================= -->
|
|
</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
|
|
<tr><td> </td><td width="100%"> <font color="#EEEEFF"
|
|
face="Georgia,Palatino"><b> <a name="customparser">Writing a custom parser
|
|
</b></font></td></tr></table><ul>
|
|
|
|
One of the simplest and most common extensions is the use of a custom parser.
|
|
As <a href="#builtinparsers">discussed previously</a>, parsers are the portion
|
|
of the CommandLine library that turns string input from the user into a
|
|
particular parsed data type, validating the input in the process.<p>
|
|
|
|
There are two ways to use a new parser:<p>
|
|
|
|
<ol>
|
|
<li>Specialize the <a href="#genericparser"><tt>cl::parser</tt></a> template for
|
|
your custom data type.<p>
|
|
|
|
This approach has the advantage that users of your custom data type will
|
|
automatically use your custom parser whenever they define an option with a
|
|
value type of your data type. The disadvantage of this approach is that it
|
|
doesn't work if your fundemental data type is something that is already
|
|
supported.<p>
|
|
|
|
<li>Write an independent class, using it explicitly from options that need
|
|
it.<p>
|
|
|
|
This approach works well in situations where you would line to parse an
|
|
option using special syntax for a not-very-special data-type. The drawback
|
|
of this approach is that users of your parser have to be aware that they are
|
|
using your parser, instead of the builtin ones.<p>
|
|
|
|
</ol><p>
|
|
|
|
To guide the discussion, we will discuss a custom parser that accepts file
|
|
sizes, specified with an optional unit after the numeric size. For example, we
|
|
would like to parse "102kb", "41M", "1G" into the appropriate integer value. In
|
|
this case, the underlying data type we want to parse into is
|
|
'<tt>unsigned</tt>'. We choose approach #2 above because we don't want to make
|
|
this the default for all <tt>unsigned</tt> options.<p>
|
|
|
|
To start out, we declare our new <tt>FileSizeParser</tt> class:<p>
|
|
|
|
<pre>
|
|
<b>struct</b> FileSizeParser : <b>public</b> cl::basic_parser<<b>unsigned</b>> {
|
|
<i>// parse - Return true on error.</i>
|
|
<b>bool</b> parse(cl::Option &O, <b>const char</b> *ArgName, <b>const</b> std::string &ArgValue,
|
|
<b>unsigned</b> &Val);
|
|
};
|
|
</pre><p>
|
|
|
|
Our new class inherits from the <tt>cl::basic_parser</tt> template class to fill
|
|
in the default, boiler plate, code for us. We give it the data type that we
|
|
parse into (the last argument to the <tt>parse</tt> method so that clients of
|
|
our custom parser know what object type to pass in to the parse method (here we
|
|
declare that we parse into '<tt>unsigned</tt>' variables.<p>
|
|
|
|
For most purposes, the only method that must be implemented in a custom parser
|
|
is the <tt>parse</tt> method. The <tt>parse</tt> method is called whenever the
|
|
option is invoked, passing in the option itself, the option name, the string to
|
|
parse, and a reference to a return value. If the string to parse is not well formed, the parser should output an error message and return true. Otherwise it should return false and set '<tt>Val</tt>' to the parsed value. In our example, we implement <tt>parse</tt> as:<p>
|
|
|
|
<pre>
|
|
<b>bool</b> FileSizeParser::parse(cl::Option &O, <b>const char</b> *ArgName,
|
|
<b>const</b> std::string &Arg, <b>unsigned</b> &Val) {
|
|
<b>const char</b> *ArgStart = Arg.c_str();
|
|
<b>char</b> *End;
|
|
|
|
<i>// Parse integer part, leaving 'End' pointing to the first non-integer char</i>
|
|
Val = (unsigned)strtol(ArgStart, &End, 0);
|
|
|
|
<b>while</b> (1) {
|
|
<b>switch</b> (*End++) {
|
|
<b>case</b> 0: <b>return</b> false; <i>// No error</i>
|
|
<b>case</b> 'i': <i>// Ignore the 'i' in KiB if people use that</i>
|
|
<b>case</b> 'b': <b>case</b> 'B': <i>// Ignore B suffix</i>
|
|
<b>break</b>;
|
|
|
|
<b>case</b> 'g': <b>case</b> 'G': Val *= 1024*1024*1024; <b>break</b>;
|
|
<b>case</b> 'm': <b>case</b> 'M': Val *= 1024*1024; <b>break</b>;
|
|
<b>case</b> 'k': <b>case</b> 'K': Val *= 1024; <b>break</b>;
|
|
|
|
default:
|
|
<i>// Print an error message if unrecognized character!</i>
|
|
<b>return</b> O.error(": '" + Arg + "' value invalid for file size argument!");
|
|
}
|
|
}
|
|
}
|
|
</pre><p>
|
|
|
|
This function implements a very simple parser for the kinds of strings we are
|
|
interested in. Although it has some holes (it allows "<tt>123KKK</tt>" for
|
|
example), it is good enough for this example. Note that we use the option
|
|
itself to print out the error message (the <tt>error</tt> method always returns
|
|
true) in order to get a nice error message (shown below). Now that we have our
|
|
parser class, we can use it like this:<p>
|
|
|
|
<pre>
|
|
<b>static</b> <a href="#cl::opt">cl::opt</a><<b>unsigned</b>, <b>false</b>, FileSizeParser>
|
|
MFS(<i>"max-file-size"</i>, <a href="#cl::desc">cl::desc</a>(<i>"Maximum file size to accept"</i>),
|
|
<a href="#cl::value_desc">cl::value_desc</a>("<i>size</i>"));
|
|
</pre><p>
|
|
|
|
Which adds this to the output of our program:<p>
|
|
|
|
<pre>
|
|
OPTIONS:
|
|
-help - display available options (--help-hidden for more)
|
|
...
|
|
<b>-max-file-size=<size> - Maximum file size to accept</b>
|
|
</pre><p>
|
|
|
|
And we can test that our parse works correctly now (the test program just prints
|
|
out the max-file-size argument value):<p>
|
|
|
|
<pre>
|
|
$ ./test
|
|
MFS: 0
|
|
$ ./test -max-file-size=123MB
|
|
MFS: 128974848
|
|
$ ./test -max-file-size=3G
|
|
MFS: 3221225472
|
|
$ ./test -max-file-size=dog
|
|
-max-file-size option: 'dog' value invalid for file size argument!
|
|
</pre><p>
|
|
|
|
It looks like it works. The error message that we get is nice and helpful, and
|
|
we seem to accept reasonable file sizes. This wraps up the "custom parser"
|
|
tutorial.<p>
|
|
|
|
|
|
<!-- ======================================================================= -->
|
|
</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
|
|
<tr><td> </td><td width="100%"> <font color="#EEEEFF"
|
|
face="Georgia,Palatino"><b> <a name="explotingexternal">Exploiting external
|
|
storage </b></font></td></tr></table><ul>
|
|
|
|
|
|
|
|
<!-- ======================================================================= -->
|
|
</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
|
|
<tr><td> </td><td width="100%"> <font color="#EEEEFF"
|
|
face="Georgia,Palatino"><b> <a name="dynamicopts">Dynamically adding command
|
|
line options </b></font></td></tr></table><ul>
|
|
|
|
|
|
|
|
|
|
|
|
<!-- *********************************************************************** -->
|
|
</ul>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<hr>
|
|
<font size=-1>
|
|
<address><a href="mailto:sabre@nondot.org">Chris Lattner</a></address>
|
|
<!-- Created: Tue Jan 23 15:19:28 CST 2001 -->
|
|
<!-- hhmts start -->
|
|
Last modified: Fri Aug 1 16:30:11 CDT 2003
|
|
<!-- hhmts end -->
|
|
</font>
|
|
</body></html>
|