A simple and easy to use command line argument parser library for Zig.
The master branch of zig-clap targets the master branch of Zig. For a version of zig-clap that targets a specific Zig release, have a look at the releases. Each release specifies the Zig version it compiles with in the release notes.
First, run the following:
zig fetch --save git+https://github.com/Hejsil/zig-clap
Then add the following to build.zig:
const clap = b.dependency("clap", .{});
exe.root_module.addImport("clap", clap.module("clap"));- Short arguments
-a- Chaining
-abcwhereaandbdoes not take values. - Multiple specifications are tallied (e.g.
-v -v).
- Chaining
- Long arguments
--long - Supports both passing values using spacing and
=(-a 100,-a=100)- Short args also support passing values with no spacing or
=(-a100) - This all works with chaining (
-ba 100,-ba=100,-ba100)
- Short args also support passing values with no spacing or
- Supports options that can be specified multiple times (
-e 1 -e 2 -e 3) - Print help message from parameter specification.
- Parse help message to parameter specification.
Automatically generated API Reference for the project can be found at https://Hejsil.github.io/zig-clap. Note that Zig autodoc is in beta; the website may be broken or incomplete.
The simplest way to use this library is to just call the clap.parse function.
const clap = @import("clap");
const std = @import("std");
const debug = std.debug;
const io = std.io;
pub fn main() !void {
var gpa = std.heap.GeneralPurposeAllocator(.{}){};
defer _ = gpa.deinit();
// First we specify what parameters our program can take.
// We can use `parseParamsComptime` to parse a string into an array of `Param(Help)`
const params = comptime clap.parseParamsComptime(
\\-h, --help Display this help and exit.
\\-n, --number <usize> An option parameter, which takes a value.
\\-s, --string <str>... An option parameter which can be specified multiple times.
\\<str>...
\\
);
// Initialize our diagnostics, which can be used for reporting useful errors.
// This is optional. You can also pass `.{}` to `clap.parse` if you don't
// care about the extra information `Diagnostics` provides.
var diag = clap.Diagnostic{};
var res = clap.parse(clap.Help, ¶ms, clap.parsers.default, .{
.diagnostic = &diag,
.allocator = gpa.allocator(),
}) catch |err| {
// Report useful error and exit
diag.report(io.getStdErr().writer(), err) catch {};
return err;
};
defer res.deinit();
if (res.args.help != 0)
debug.print("--help\n", .{});
if (res.args.number) |n|
debug.print("--number = {}\n", .{n});
for (res.args.string) |s|
debug.print("--string = {s}\n", .{s});
for (res.positionals) |pos|
debug.print("{s}\n", .{pos});
}
The result will contain an args field and a positionals field. args will have one field
for each none positional parameter of your program. The name of the field will be the longest
name of the parameter.
The fields in args are typed. The type is based on the name of the value the parameter takes.
Since --number takes a usize the field res.args.number has the type usize.
Note that this is only the case because clap.parsers.default has a field called usize which
contains a parser that returns usize. You can pass in something other than
clap.parsers.default if you want some other mapping.
const clap = @import("clap");
const std = @import("std");
const debug = std.debug;
const io = std.io;
const process = std.process;
pub fn main() !void {
var gpa = std.heap.GeneralPurposeAllocator(.{}){};
defer _ = gpa.deinit();
// First we specify what parameters our program can take.
// We can use `parseParamsComptime` to parse a string into an array of `Param(Help)`
const params = comptime clap.parseParamsComptime(
\\-h, --help Display this help and exit.
\\-n, --number <INT> An option parameter, which takes a value.
\\-a, --answer <ANSWER> An option parameter which takes an enum.
\\-s, --string <STR>... An option parameter which can be specified multiple times.
\\<FILE>...
\\
);
// Declare our own parsers which are used to map the argument strings to other
// types.
const YesNo = enum { yes, no };
const parsers = comptime .{
.STR = clap.parsers.string,
.FILE = clap.parsers.string,
.INT = clap.parsers.int(usize, 10),
.ANSWER = clap.parsers.enumeration(YesNo),
};
var diag = clap.Diagnostic{};
var res = clap.parse(clap.Help, ¶ms, parsers, .{
.diagnostic = &diag,
.allocator = gpa.allocator(),
}) catch |err| {
diag.report(io.getStdErr().writer(), err) catch {};
return err;
};
defer res.deinit();
if (res.args.help != 0)
debug.print("--help\n", .{});
if (res.args.number) |n|
debug.print("--number = {}\n", .{n});
if (res.args.answer) |a|
debug.print("--answer = {s}\n", .{@tagName(a)});
for (res.args.string) |s|
debug.print("--string = {s}\n", .{s});
for (res.positionals) |pos|
debug.print("{s}\n", .{pos});
}
The streaming.Clap is the base of all the other parsers. It's a streaming parser that uses an
args.Iterator to provide it with arguments lazily.
const clap = @import("clap");
const std = @import("std");
const debug = std.debug;
const io = std.io;
const process = std.process;
pub fn main() !void {
const allocator = std.heap.page_allocator;
// First we specify what parameters our program can take.
const params = [_]clap.Param(u8){
.{
.id = 'h',
.names = .{ .short = 'h', .long = "help" },
},
.{
.id = 'n',
.names = .{ .short = 'n', .long = "number" },
.takes_value = .one,
},
.{ .id = 'f', .takes_value = .one },
};
var iter = try process.ArgIterator.initWithAllocator(allocator);
defer iter.deinit();
// Skip exe argument
_ = iter.next();
// Initialize our diagnostics, which can be used for reporting useful errors.
// This is optional. You can also leave the `diagnostic` field unset if you
// don't care about the extra information `Diagnostic` provides.
var diag = clap.Diagnostic{};
var parser = clap.streaming.Clap(u8, process.ArgIterator){
.params = ¶ms,
.iter = &iter,
.diagnostic = &diag,
};
// Because we use a streaming parser, we have to consume each argument parsed individually.
while (parser.next() catch |err| {
// Report useful error and exit
diag.report(io.getStdErr().writer(), err) catch {};
return err;
}) |arg| {
// arg.param will point to the parameter which matched the argument.
switch (arg.param.id) {
'h' => debug.print("Help!\n", .{}),
'n' => debug.print("--number = {s}\n", .{arg.value.?}),
// arg.value == null, if arg.param.takes_value == .none.
// Otherwise, arg.value is the value passed with the argument, such as "-a=10"
// or "-a 10".
'f' => debug.print("{s}\n", .{arg.value.?}),
else => unreachable,
}
}
}
Currently, this parser is the only parser that allows an array of Param that
is generated at runtime.
The help prints a simple list of all parameters the program can take. It expects the
Id to have a description method and an value method so that it can provide that
in the output. HelpOptions is passed to help to control how the help message is
printed.
const clap = @import("clap");
const std = @import("std");
pub fn main() !void {
var gpa = std.heap.GeneralPurposeAllocator(.{}){};
defer _ = gpa.deinit();
const params = comptime clap.parseParamsComptime(
\\-h, --help Display this help and exit.
\\-v, --version Output version information and exit.
\\
);
var res = try clap.parse(clap.Help, ¶ms, clap.parsers.default, .{
.allocator = gpa.allocator(),
});
defer res.deinit();
// `clap.help` is a function that can print a simple help message. It can print any `Param`
// where `Id` has a `describtion` and `value` method (`Param(Help)` is one such parameter).
// The last argument contains options as to how `help` should print those parameters. Using
// `.{}` means the default options.
if (res.args.help != 0)
return clap.help(std.io.getStdErr().writer(), clap.Help, ¶ms, .{});
}
$ zig-out/bin/help --help
-h, --help
Display this help and exit.
-v, --version
Output version information and exit.
The usage prints a small abbreviated version of the help message. It expects the Id
to have a value method so it can provide that in the output.
const clap = @import("clap");
const std = @import("std");
pub fn main() !void {
var gpa = std.heap.GeneralPurposeAllocator(.{}){};
defer _ = gpa.deinit();
const params = comptime clap.parseParamsComptime(
\\-h, --help Display this help and exit.
\\-v, --version Output version information and exit.
\\ --value <str> An option parameter, which takes a value.
\\
);
var res = try clap.parse(clap.Help, ¶ms, clap.parsers.default, .{
.allocator = gpa.allocator(),
});
defer res.deinit();
// `clap.usage` is a function that can print a simple help message. It can print any `Param`
// where `Id` has a `value` method (`Param(Help)` is one such parameter).
if (res.args.help != 0)
return clap.usage(std.io.getStdErr().writer(), clap.Help, ¶ms);
}
$ zig-out/bin/usage --help
[-hv] [--value <str>]