FBB::Arg - A singleton class interfacing command line
arguments
#include <bobcat/arg>
Linking option: -lbobcat
Singleton class (see Gamma et al., 1995) built around
getopt_long()(3). The class handles short- and long command-line
options,
FBB
All constructors, members, operators and manipulators, mentioned in this
man-page, are defined in the namespace FBB.
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.
- o
- None: the long option does not use an argument;
- o
- Required: the long option requires an argument value;
- o
- Optional: the long option may optionally be provided with an
argument value;
These values are used when defining long options (like
--version), which are defined as objects of 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:
- o
- 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 specifying the -- characters which are only required when
specifying a long option when calling a program).
- o
- 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 specifying the -- characters which are only required when
specifying a long option when calling a program).
To define long options use the following procedure:
- o
- First, construct an array
FBB::Arg::LongOption longOptions[] = { c1, c2, ..., cn };
Where c1, c2, ..., cn are n constructor invocations of
FBB::Arg::LongOption() constructors
- o
- Next, pass longOptions, LongOptions + n as arguments to an
Arg::initialize member that supports long options.
Objects of the class LongOptions are normally used
internally by the Arg object, but they can also be used outside of
the Arg object. For that situation the following members are
available:
- o
- std::string const &longName() const:
returns the LongOption’s long option name;
- o
- 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).
Since the class Arg is a singleton there are no
public constructors. Instead, static members are available to initialize and
to access the single FBB::Arg object.
All initialize members initialize the FBB::Arg
singleton, and can only be called once. An exception is thrown when called
multiple times. All initialize members return a reference to the
initialized Arg singleton object.
All initialize members define the parameters argc
and argv which are interpreted as main’s argc
and argv parameters. When an argv element points to two
consecutive dashes (--) then that element is ignored, and all of
argv’s subsequent elements are considered arguments instead of
options.
- o
- FBB::Arg &Arg::initialize(char const *optstring, int argc, char
**argv):
The parameter optstring is a null-terminated byte string (NTBS)
optionally starting with a + character, but otherwise containing option
characters. One or two colons may be postfixed to option characters:
- o
- a single colon (:) indicates that the option requires an option
value.
- o
- a double colon (::) indicates that the option has an optional argument.
With short options the option value is considered absent unless it is
attached to the short option (e.g., -tvalue). Long options
optionally accepting arguments should always immediately be followed by an
assignment character (=), immediately followed by the option’s
value (which must start with a non-blank character). E.g., --value=
indicates an absent option value, --value=text indicates the
option’s value equals text. If an option value itself
contains blanks, it must be surrounded by single or double quotes (e.g.,
-t’this value’, or --text=’this
value’). The surrounding quotes are not part of the
option’s value.
- When optstring’s first character is + then all non-specified
options are considered arguments, appearing in the final arguments list at
their current argument positions. E.g., when optstring is
+ab and no long options are defined, then calling
prog -a -z -b -yvalue --long arg1 arg2
results in the member argv returning a vector containing the elements
-z, -yvalue, --long, arg1, and arg2. If
optstring’s first character isn’t + and an undefined
option is encountered then an exception is thrown.
- o
- FBB::Arg &Arg::initialize(int accept, char const *optstring,
int argc, char **argv):
Acts like the previous member, but in addition defines the parameter
accept specifying an option character from where all subsequent
arguments and options are considered arguments. To ignore accept
the value 0 (not the character ’0’) can be specified or an
initialize members can be used that does not define an
accept parameter.
- When arguments contain both an accept option and two consecutive
dashes then the first one is interpreted, resulting in all remaining
argv elements being interpreted as mere arguments. For example,
when specifying initialize(’t’, ...) and calling
prog one -ttwo -c -- three
then the member argv returns a vector containing the elements one,
-tttwo, -c, --, and three (see also the member
beyondDashes below).
- o
- FBB::Arg &Arg::initialize(char const *optstring,
Arg::LongOption const *const begin, Arg::LongOption const *const
end, int argc, char **argv):
- Acts like the first Arg::initialize member, but in addition defines
two parameters specifying the range of elements of an array of
Arg::LongOption objects specifying long options. The parameter
begin points to the first element of the range, the parameter
end points just beyond the last element of the range. E.g., after
defining
FBB::Arg::LongOption longOptions[] = { c1, c2, ..., cn };
the arguments passed to begin and end could be specified as
initialize(..., longOptions, longOptions + size(longOptions), ...);
- o
- FBB::Arg &Arg::initialize(char accept, char const *optstring,
LongOption const *const begin, LongOption const *const end,
int argc, char **argv):
- Acts like the previous Arg::initialize member, but in addition
defines an accept parameter as defined by the second
Arg::initialize member.
- o
- FBB::Arg &Arg::instance():
Once an Arg::initialize member has been called this member can be
called from anywhere in the program (and it can be called multiple times),
returning a reference to the initialized Arg object.
- If it is called before an Arg::initialize member has been called an
exception is thrown.
- o
- char const *operator[](size_t idx) const:
Returns argument[idx], after all options have been removed. 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].
- o
- string const &argv0() const:
Returns the program’s name as specified by argv[0] (see also
the member basename);
- o
- char const **argPointers() const:
Returns argv-like set of pointers to all remaining arguments. Element
nArgs() + 1 is a 0-pointer. The first nArgs() elements point
to the respective values of the NTBS arguments that were passed to the
program, after having removed the options.
- The caller is responsible for returning the array of pointers returned by
this member to the common pool, but the caller should not delete the NTBSs
to which the pointers point as illustrated by the following two
statements:
char const **ptr = Arg::instance().argPointers();
delete[] ptr; // don’t delete ptr[idx] elements!
- o
- std::vector<std::string> const &args() const:
Returns a vector of strings containing all arguments after having removed
all options. The program’s name (argv[0]) is NOT included
here: its first element refers to the first ARGUMENT, e.g., the
program’s argv[1];
- o
- std::string const &basename() const:
Returns the program’s basename (i.e., argv0()’s value
beyond the last directory separator);
- o
- std::vector<std::string>::const_iterator begin() const:
Returns the iterator to the program’s first argument (i.e.,
args().begin()). This member, in combination with the member
end, allows processing of all arguments by generic algorithms;
- o
- size_t beyondDashes() const:
Returns the index of the first argument beyond the -- argument or
returns the index of the accept argument (whichever comes first) or
returns nArgs() if no -- or accept argument was
encountered. See also the member nArgs below;
- o
- std::vector<std::string>::const_iterator end() const:
Returns the iterator pointing beyond the program’s last argument
(i.e., args().end()). This member, in combination with the member
begin, allows processing of all arguments by generic
algorithms;
- o
- void help() const:
If the member versionHelp (see below) was 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 exception is thrown;
- o
- size_t nArgs() const:
Returns the number of arguments after having removed the options (i.e., it
returns args().size()). Note that the program’s name is not
counted here;
- o
- size_t nLongOptions() const:
Returns the number of long options not having short option synonyms.
Multiply specified long options are each counted;
- o
- 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;
- o
- size_t option(int option) const:
Returns the number of times `option’ was specified (or its long
option synonym, if defined);
- o
- 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;
- o
- 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;
- o
- 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;
- o
- 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;
- o
- 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;
- o
- 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;
- o
- 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;
- o
- 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.
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;
}
bobcat/arg - defines the class interface
- o
- https://fbb-git.gitlab.io/bobcat/: gitlab project page;
- o
- bobcat_6.02.02-x.dsc: detached signature;
- o
- bobcat_6.02.02-x.tar.gz: source archive;
- o
- bobcat_6.02.02-x_i386.changes: change log;
- o
- libbobcat1_6.02.02-x_*.deb: debian package containing the
libraries;
- o
- libbobcat1-dev_6.02.02-x_*.deb: debian package containing the
libraries, headers and manual pages;
Bobcat is an acronym of `Brokken’s Own Base Classes And
Templates’.
This is free software, distributed under the terms of the GNU
General Public License (GPL).
Frank B. Brokken (f.b.brokken@rug.nl).