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89 lines
3.1 KiB
89 lines
3.1 KiB
2 months ago
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Option parser
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=============
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Libucw contains a parser of command-line options, more versatile and
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easier to use than the usual `getopt()` and `getopt_long()`. It follows the
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traditional UNIX conventions of option syntax, but the options are defined in
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a declarative way, similar in spirit to our <<conf:,configuration file
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parser>>.
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- <<example,Example>>
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- <<anatomy,Anatomy of options>>
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- <<opt_h,ucw/opt.h>>
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* <<classes,Option classes>>
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* <<opt_item,Option definitions>>
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* <<flags,Option flags>>
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* <<macros,Macros for declaration of options>>
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* <<positional,Positional arguments>>
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* <<func,Functions>>
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* <<conf,Cooperating with configuration file parser>>
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* <<hooks,Hooks>>
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[[example]]
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Example
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-------
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Let us start with a simple example: a program with several options and
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one mandatory positional argument.
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#include <ucw/lib.h>
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#include <ucw/opt.h>
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int english;
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int sugar;
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int verbose;
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char *tea_name;
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static struct opt_section options = {
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OPT_ITEMS {
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OPT_HELP("A simple tea boiling console."),
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OPT_HELP("Usage: teapot [options] name-of-the-tea"),
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OPT_HELP(""),
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OPT_HELP("Options:"),
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OPT_HELP_OPTION,
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OPT_BOOL('e', "english-style", english, 0, "\tEnglish style (with milk)"),
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OPT_INT('s', "sugar", sugar, OPT_REQUIRED_VALUE, "<spoons>\tAmount of sugar (in teaspoons)"),
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OPT_INC('v', "verbose", verbose, 0, "\tVerbose (the more -v, the more verbose)"),
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OPT_STRING(OPT_POSITIONAL(1), NULL, tea_name, OPT_REQUIRED, ""),
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OPT_END
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}
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};
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int main(int argc, char **argv)
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{
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opt_parse(&options, argv+1);
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return 0;
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}
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[[anatomy]]
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Anatomy of options
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------------------
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Most options have the following properties:
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- <<classes,Option class>> defining overall behavior of the option
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- Short name: one character. Set to 0 if the option has no short form.
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Alternatively, the short name can refer to a <<positional,positional argument>>.
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- Long name: an arbitrary string. Set to NULL if the option has no long form.
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- Variable, where the value of the option shall be stored, together with
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its <<conf:enum_cf_type,data type>>. The type is either one of the conventional
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types (`int`, `uint`, etc.), an extended type providing its own parser
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function via <<xtypes:struct_xtype,`xtype`>>, or an obsolete user-type
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defined by <<conf:struct_cf_user_type,`cf_user_type`>>.
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- <<flags,Flags>> further specifying behavior of the option (whether it is mandatory,
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whether it carries a value, whether it can be set repeatedly, etc.).
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- Help text, from which the help displayed to the user is constructed.
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- Extra data specific for the particular class.
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The help is generated in a three-column format. The first column contains the
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short names, then come the long names, and finally option descriptions.
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The help text starts in column 2 (where it can describe the option's argument);
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you can use the tab character to advance to the next column. When a newline
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character appears, the text continues on the next line in column 1.
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[[opt_h]]
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ucw/opt.h
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---------
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This header file contains the public interface of the option parser module.
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!!ucw/opt.h
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