FBB::Arg(3bobcat)
Command Line Arguments
(libbobcat-dev_5.07.03)
2005-2021
NAME
FBB::Arg - A singleton class interfacing command line arguments
SYNOPSIS
#include <bobcat/arg>
Linking option: -lbobcat
DESCRIPTION
Singleton class (see Gamma et al., 1995) built around getopt()(3)
and getopt_long()(3). The class handles short- and long command-line
options,
NAMESPACE
FBB
All constructors, members, operators and manipulators, mentioned in this
man-page, are defined in the namespace FBB.
INHERITS FROM
-
ENUMERATION
The FBB::Arg::Type enumeration is defined by the FBB::Arg
class. It is used to specify whether or not long options require arguments. It
defines the following values: None, Required, Optional.
- None: the long option does not use an argument;
- Required: the long option requires an argument value;
- Optional: the long option may optionally be provided with an
argument value;
These values are used when constructing objects of the following (nested)
class FBB::Arg::LongOption.
THE NESTED CLASS FBB::Arg::LongOption
Long options are defined using objects of the nested class
FBB::Arg::LongOption. This class provides the following constructors:
- FBB::Arg::LongOption(char const *name, FBB::Arg::Type type =
FBB::Arg::None):
This constructor is used to define a long option for which no
corresponding short option is defined. The parameter name is the
name of the long option (without prefixing the -- characters,
which are required when specifying the long option).
- FBB::Arg::LongOption(char const *name, int optionChar):
This constructor is used to define a long option for which a
corresponding short option is defined. The parameter name is the
name of the long option (without prefixing the -- characters,
which are required when specifying the long option).
In a program, long options may be specified as follows:
The class LongOptions is primarily used internally by the Arg
object, but it can also be used outside of the Arg object. For that
situation the following members are provided:
- std::string const &longName() const:
returns the LongOption's long option name;
- int optionChar() const:
returns the LongOption's option character (or one of the
Arg::Type enumeration values if there is no option character
associated with the LongOption).
CONSTRUCTORS
Since the class is a Singleton there are no public
constructors. Instead, static members are offered for initializing and
accessing the single FBB::Arg object.
STATIC MEMBERS
OVERLOADED OPERATOR
- char const *operator[](size_t idx) const:
Returns argument[idx], after having removed all specified options.
It returns 0 if no arg[x] is available. The program's name
(argv[0]) is NOT counted here: index 0 refers to the first
ARGUMENT, e.g., the program's argv[1].
NON-STATIC MEMBER FUNCTIONS
- char const **argPointers() const:
Returns argv-like set of pointers to all remaining arguments. The
last element is guaranteed to be a 0-pointer. The first nArg()
elements point to the respective values of the NTBS arguments that
were passed to the program.
The caller is responsible for returning the array of pointers to the
common pool, but should not delete the C-strings to which the pointers
point. The following two statements illustrate this:
char const **ptr = Arg::instance().argPointers();
delete[] ptr;
- std::string const &basename() const:
Returns the program's basename.
- size_t beyondDashes() const:
Returns the index of the first argument after a -- argument or
returns nArgs() if no -- argument was encountered.
A -- argument ends Arg's argument processing, and all arguments
beyond the first -- argument are kept `as is'. The
beyondDashes member returns the index of the first argument beyond
the -- argument, which itself is removed from the remaining set of
arguments.
- void help() const:
If the member versionHelp (see below) has been called then this
member calls the usage function that was passed to
versionHelp. If versionHelp has not been called (i.e., if no
usage function has been specified) an FBB::Exception is
thrown.
- size_t nArgs() const:
Returns the number of arguments left after option-removal. The
program name argv[0] is NOT counted here.
- size_t nLongOptions() const:
Returns the number of long options not having short option synonyms If
long options are multiply specified, then each specification is
counted.
- size_t nOptions() const:
Returns the number of specified single character options. If short
options have long option synonyms, then these long option synonyms are
counted as if they were specified as single character options. If
single character options (or their long option synonyms) are multiply
specified, then each specification is separately counted.
- size_t option(int option) const:
Returns the number of times `option' was specified (or its long option
synonym, if defined).
- size_t option(std::string const &options) const:
Returns the number of times each of the options specified in the `option'
argument were specified (or their long option synonyms). Note that
each character in options must specify a single-character option.
- size_t option(string *value, int option) const:
Returns the number of times the provided option (or its long option
synonym) was present. If the return value is non-zero then the value
of the first occurrence of this option is stored in *value, which
is left untouched if `option' was not present. The parameter value
may be initialized to 0 if the option does not have a value or if the
option's value should not be stored.
- size_t option(size_t idx, string *value, int option) const:
Returns the number of times the provided option (or its long option
synonym) was present. If the return value is non-zero then the value
of the idxth occurrence (0-based offset) of this option is stored
in *value, which is left untouched if `option' was not present or
if idx is or exceeds the number of specifications of the provided
option. 0 may be specified for value if the option does not have a
value or if the value should not be stored.
- size_t option(size_t *idx, string *value, int option) const:
Returns the number of times the provided option (or its long option
synonym) was present. If the return value is non-zero then the offset
(within the series of option specifications) of the first option
having a non-empty option value is returned in *idx, while its
option value is stored in *value. Both *value and *idx are
left untouched if `option' was not present. 0 may be specified for
value if the option does not have a value or if the value should
not be stored.
- size_t option(string *value, char const *longOption) const:
Returns the number of times the specified long option (not having a
single-character synonym) was present. Its value is then stored in
*value, which is left untouched if the long option was not
present. 0 may be specified for value if the option does not have
a value or if the value should not be stored.
- size_t option(size_t idx, string *value,
char const * longOption) const:
Returns the number of times the provided long option (not having a
single-character synonym) was present. If the return value is non-zero
then the value of the idxth occurrence (0-based offset) of this
long option is stored in *value, which is left untouched if the
long option was not present or if idx is or exceeds the number of
specifications of the provided long option. 0 may be specified for
value if the long option does not have a value or if the value
should not be stored.
- size_t option(size_t *idx, string *value, int longOption) const:
Returns the number of times the provided long option (not having a
single-character synonym) was present. If the return value is non-zero
then the offset (within the series of this long option specifications)
of the first long option having a non-empty option value is returned
in *idx, while its option value is stored in *value. Both
*value and *idx are left untouched if long option was not
present. 0 may be specified for value if the long option does not
have a value or if the value should not be stored.
- void versionHelp(void (*usage)(std::string const &progname),
char const *version, size_t minArgs, int helpFlag = 'h',
int versionFlag = 'v') const:
If the helpFlag was specified usage() is called with
argument basename() whereafter the program throws int 0.
If versionFlag was specified the program's name (using basename())
and version is displayed to std::cout whereafter the program
throws int 0.
If there are fewer arguments than minArgs usage() is called with
argument basename() and the program ends with exit value 1.
Note that versionhelp compares minArgs against nArgs. If
minArgs should be compaired against the number of arguments up to
a possible `--' argument (i.e., beyondDashes' return value), then
add nArgs() - beyondDashes() to the minArg argument. E.g.,
arg.versionHelp(usage, version, 2 + arg.nArgs()
- arg.beyondDashes());
The address of the usage() function, the current version and the
minimum number of arguments must be specified. Default argument values
are provided for the option flags.
EXAMPLE
The following example illustrates defining long options and shows an
initialization. It is not a full-fledched example in the sense of a small
runnable program.
#include <bobcat/arg>
using namespace FBB;
using namespace std;
namespace // the anonymous namespace can be used here
{
Arg::LongOption longOptions[] =
{
Arg::LongOption{"debug"},
Arg::LongOption{"filenames", 'f'},
Arg::LongOption{"help", 'h'},
Arg::LongOption{"version", 'v'},
};
auto longEnd = longOptions + size(longOptions);
}
int main(int argc, char **argv)
try
{
Arg &arg = Arg::initialize("df:hv",
longOptions, longEnd,
argc, argv);
// code using arg, etc.
}
catch (exception const &err) // handle exceptions
{
cerr << err.what() << '\n';
return 1;
}
FILES
bobcat/arg - defines the class interface
SEE ALSO
bobcat(7)
BUGS
None Reported.
BOBCAT PROJECT FILES
- https://fbb-git.gitlab.io/bobcat/: gitlab project page;
- bobcat_5.07.03-x.dsc: detached signature;
- bobcat_5.07.03-x.tar.gz: source archive;
- bobcat_5.07.03-x_i386.changes: change log;
- libbobcat1_5.07.03-x_*.deb: debian package containing the
libraries;
- libbobcat1-dev_5.07.03-x_*.deb: debian package containing the
libraries, headers and manual pages;
BOBCAT
Bobcat is an acronym of `Brokken's Own Base Classes And Templates'.
COPYRIGHT
This is free software, distributed under the terms of the
GNU General Public License (GPL).
AUTHOR
Frank B. Brokken (f.b.brokken@rug.nl).