Getopt for Erlang ================= Command-line parsing module that uses a syntax similar to that of GNU *getopt*. Requirements ------------ You should only need a somewhat recent version of Erlang/OTP. The module has been tested with Erlang R13B, R14B and R15B. You also need a recent version of [rebar](http://github.com/basho/rebar) in the system path. If you're going to run the unit tests you need the latest version of rebar to make sure that the latest version of *getopt* is being used. rebar already includes a compiled copy of the ``getopt`` module in its own binary file and will give precedence to its own modules over the ones in the project. Installation ------------ To compile the module you simply run ``make``. To run the unit tests run ``make test``. To run the example module run ``make example``. To build the (very) limited documentation run ``make doc``. Usage ----- The *getopt* module provides four functions: ``` erlang parse([{Name, Short, Long, ArgSpec, Help}], Args :: string() | [string()]) -> {ok, {Options, NonOptionArgs}} | {error, {Reason, Data}} tokenize(CmdLine :: string()) -> [string()] usage([{Name, Short, Long, ArgSpec, Help}], ProgramName :: string()) -> ok usage([{Name, Short, Long, ArgSpec, Help}], ProgramName :: string(), CmdLineTail :: string()) -> ok usage([{Name, Short, Long, ArgSpec, Help}], ProgramName :: string(), CmdLineTail :: string(), OptionsTail :: [{string(), string}]) -> ok ``` The ``parse/2`` function receives a list of tuples with the command line option specifications. The type specification for the tuple is: ``` erlang -type arg_type() :: 'atom' | 'binary' | 'boolean' | 'float' | 'integer' | 'string'. -type arg_value() :: atom() | binary() | boolean() | float() | integer() | string(). -type arg_spec() :: arg_type() | {arg_type(), arg_value()} | undefined. -type option_spec() :: { Name :: atom(), Short :: char() | undefined, Long :: string() | undefined, ArgSpec :: arg_spec(), Help :: string() | undefined }. ``` The elements of the tuple are: - ``Name``: name of the option. - ``Short``: character for the short option (e.g. $i for -i). - ``Long``: string for the long option (e.g. "info" for --info). - ``ArgSpec``: data type and optional default value the argument will be converted to. - ``Help``: help message that is shown for the option when ``usage/2`` is called. e.g. ``` erlang {port, $p, "port", {integer, 5432}, "Database server port"} ``` The second parameter receives the list of arguments as passed to the ``main/1`` function in escripts or the unparsed command line as a string. If the function is successful parsing the command line arguments it will return a tuple containing the parsed options and the non-option arguments. The options will be represented by a list of key-value pairs with the ``Name`` of the option as *key* and the argument from the command line as *value*. If the option doesn't have an argument, only the atom corresponding to its ``Name`` will be added to the list of options. For the example given above we could get something like ``{port, 5432}``. The non-option arguments are just a list of strings with all the arguments that did not have corresponding options. e.g. Given the following option specifications: ``` erlang OptSpecList = [ {host, $h, "host", {string, "localhost"}, "Database server host"}, {port, $p, "port", integer, "Database server port"}, {dbname, undefined, "dbname", {string, "users"}, "Database name"}, {xml, $x, undefined, undefined, "Output data in XML"}, {verbose, $v, "verbose", integer, "Verbosity level"}, {file, undefined, undefined, string, "Output file"} ]. ``` And this command line: ``` erlang Args = "-h myhost --port=1000 -x myfile.txt -vvv dummy1 dummy2" ``` Which could also be passed in the format the ``main/1`` function receives the arguments in escripts: ``` erlang Args = ["-h", "myhost", "--port=1000", "-x", "file.txt", "-vvv", "dummy1", "dummy2"]. ``` The call to ``getopt:parse/2``: ``` erlang getopt:parse(OptSpecList, Args). ``` Will return: ``` erlang {ok,{[{host,"myhost"}, {port,1000}, xml, {file,"file.txt"}, {dbname,"users"}, {verbose,3}], ["dummy1","dummy2"]}} ``` The ``tokenize/1`` function will separate a command line string into tokens, taking into account whether an argument is single or double quoted, a character is escaped or if there are environment variables to be expanded. e.g.: ``` erlang getopt:tokenize(" --name John\\ Smith --path \"John's Files\" -u ${USER}"). ``` Will return something like: ``` erlang ["--name","John Smith","--path","John's Files","-u","jsmith"] ``` The other functions exported by the ``getopt`` module (``usage/2``, ``usage/3`` and ``usage/4``) are used to show the command line syntax for the program. For example, given the above-mentioned option specifications, the call to ``getopt:usage/2``: ``` erlang getopt:usage(OptSpecList, "ex1"). ``` Will show (on *standard_error*): Usage: ex1 [-h <host>] [-p <port>] [--dbname <dbname>] [-x] [-v] <file> -h, --host Database server host -p, --port Database server port --dbname Database name -x Output data in XML -v Verbosity level <file> Output file This call to ``getopt:usage/3`` will add a string after the usage command line: ``` erlang getopt:usage(OptSpecList, "ex1", "[var=value ...] [command ...]"). ``` Will show (on *standard_error*): Usage: ex1 [-h <host>] [-p <port>] [--dbname <dbname>] [-x] [-v <verbose>] <file> [var=value ...] [command ...] -h, --host Database server host -p, --port Database server port --dbname Database name -x Output data in XML -v, --verbose Verbosity level <file> Output file Whereas this call to ``getopt:usage/3`` will also add some lines to the options help text: ``` erlang getopt:usage(OptSpecList, "ex1", "[var=value ...] [command ...]", [{"var=value", "Variables that will affect the execution (e.g. debug=1)"}, {"command", "Commands that will be executed (e.g. count)"}]). ``` Will show (on *standard_error*): Usage: ex1 [-h <host>] [-p <port>] [--dbname <dbname>] [-x] [-v <verbose>] <file> [var=value ...] [command ...] -h, --host Database server host -p, --port Database server port --dbname Database name -x Output data in XML -v, --verbose Verbosity level <file> Output file var=value Variables that will affect the execution (e.g. debug=1) command Commands that will be executed (e.g. count) Command-line Syntax ------------------- The syntax supported by the ``getopt`` module is very similar to that followed by GNU programs, which is described [here](http://www.gnu.org/s/libc/manual/html_node/Argument-Syntax.html). Options can have both short (single character) and long (string) option names. A short option can have the following syntax: -a Single option 'a', no argument or implicit boolean argument -a foo Single option 'a', argument "foo" -afoo Single option 'a', argument "foo" -abc Multiple options: 'a'; 'b'; 'c' -bcafoo Multiple options: 'b'; 'c'; 'a' with argument "foo" -aaa Multiple repetitions of option 'a' A long option can have the following syntax: --foo Single option 'foo', no argument --foo=bar Single option 'foo', argument "bar" --foo bar Single option 'foo', argument "bar" Argument Types -------------- The arguments allowed for options are: *atom*; *binary*; *boolean*; *float*; *integer*; *string*. The ``getopt`` module checks every argument to see if it can be converted to its correct type. In the case of boolean arguments, the following values (in lower or upper case) are considered ``true``: *true*; *t*; *yes*; *y*; *on*; *enabled*; *1*. These ones are considered ``false``: *false*; *f*; *no*; *n*; *off*; *disabled*; *0*. Numeric arguments can only be negative when passed as part of an assignment expression. e.g. ``--increment=-100`` is a valid expression; whereas ``--increment -100`` is invalid Implicit Arguments ------------------ The arguments for options with the *boolean* and *integer* data types can sometimes be omitted. In those cases the value assigned to the option is *true* for *boolean* arguments and *1* for integer arguments. Multiple Repetitions -------------------- An option can be repeated several times, in which case there will be multiple appearances of the option in the resulting list. The only exceptions are short options with integer arguments. In that particular case, each appearance of the short option within a single command line argument will increment the number that will be returned for that specific option. e.g. Given an option specification list with the following format: ``` erlang OptSpecList = [ {define, $D, "define", string, "Define a variable"}, {verbose, $v, "verbose", integer, "Verbosity level"} ]. ``` The following invocation: ``` erlang getopt:parse(OptSpecList, "-DFOO -DVAR1=VAL1 -DBAR --verbose --verbose=3 -v -vvvv dummy"). ``` would return: ``` erlang {ok,{[{define,"FOO"}, {define,"VAR1=VAL1"}, {define,"BAR"}, {verbose,1}, {verbose,3}, {verbose,1}, {verbose,4}], ["dummy"]}} ``` Positional Options ------------------ We can also have options with neither short nor long option names. In this case, the options will be taken according to their position in the option specification list passed to ``getopt:/parse2``. For example, with the following option specifications: ``` erlang OptSpecList = [ {xml, $x, "xml", undefined, "Output data as XML"}, {dbname, undefined, undefined, string, "Database name"}, {output_file, undefined, undefined, string, "File where the data will be saved to"} ]. ``` This call to ``getopt:parse/2``: ``` erlang getopt:parse(OptSpecList, "-x mydb file.out dummy dummy"). ``` Will return: ``` erlang {ok,{[xml,{dbname,"mydb"},{output_file,"file.out"}], ["dummy","dummy"]}} ``` Option Terminators ------------------ The string ``--`` is considered an option terminator. This means that all the command-line arguments after it are considered non-option arguments and will be returned without being evaluated even if they follow the *getopt* syntax. e.g. This invocation using the first option specification list in the document: ``` erlang getopt:parse(OptSpecList, "-h myhost -p 1000 -- --dbname mydb dummy"). ``` will return: ``` erlang {ok,{[{host,"myhost"}, {port,1000},{dbname,"users"}], ["--dbname","mydb","dummy"]}} ``` Notice that the *dbname* option was assigned the value ``users`` instead of ``mydb``. This happens because the option terminator prevented *getopt* from evaluating it and the default value was assigned to it. Non-option Arguments -------------------- The single ``-`` character is always considered as a non-option argument. e.g. This invocation using the specification list from the previous example: ``` erlang getopt:parse(OptSpecList, "-h myhost -p 1000 - --dbname mydb dummy"). ``` will return: ``` erlang {ok,{[{host,"myhost"}, {port,1000}, {dbname,"mydb"}], ["-","dummy"]}} ``` Arguments with embedded whitespace ---------------------------------- Arguments that have embedded whitespace have to be quoted with either single or double quotes to be considered as a single argument. e.g. Given an option specification list with the following format: ``` erlang OptSpecList = [ {define, $D, "define", string, "Define a variable"}, {user, $u, "user", string, "User name"} ]. ``` The following invocation: ``` erlang getopt:parse(OptSpecList, "-D'FOO=VAR 123' --define \"VAR WITH SPACES\" -u\"my user name\""). ``` would return: ``` erlang {ok,{[{define,"FOO=VAR 123"}, {define,"VAR WITH SPACES"}, {user,"my user name"}], []}} ``` When parsing a command line with unclosed quotes the last argument will be a single string starting at the position where the last quote was entered. e.g. The following invocation: ``` erlang getopt:parse(OptSpecList, "--user ' my user ' \"argument with unclosed quotes"). ``` would return: ``` erlang {ok,{[{user," my user "}], ["argument with unclosed quotes"]}} ``` Environment variable expansion ------------------------------ `getopt:parse/2` will expand environment variables when used with a command line that is passed as a single string. The formats that are supported for environment variable expansion are: - $VAR (simple Unix/bash format) - ${VAR} (full Unix/bash format) - %VAR% (Windows format) If a variable is not present in the environment it will not be expanded. Variables can be expanded within double-quoted and free arguments. *getopt* will not expand environment variables within single-quoted arguments. e.g. Given the following option specification list: ``` erlang OptSpecList = [ {path, $p, "path", string, "File path"} ]. ``` The following invocation: ``` erlang getopt:parse(OptSpecList, "--path ${PATH} $NONEXISTENT_DUMMY_VAR"). ``` would return (depending on the value of your PATH variable) something like: ``` erlang {ok,{[{path, "/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"}], ["$NONEXISTENT_DUMMY_VAR"]}} ``` Currently, *getopt* does not perform wildcard expansion of file paths. Escaping arguments ================== Any character can be escaped by prepending the \ (backslash) character to it. e.g. ``` erlang getopt:parse(OptSpecList, "--path /john\\'s\\ files dummy"). ``` Will return: ``` erlang {ok,{[{path,"/john's files"}],["dummy"]}} ```