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# zig-clap
A simple and easy to use command line argument parser library for Zig.
## Features
* Short arguments `-a`
* Chaining `-abc` where `a` and `b` does not take values.
* 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`)
* Print help message from parameter specification.
* Parse help message to parameter specification.
## Examples
### `StreamingClap`
The `StreamingClap` is the base of all the other parsers. It's a streaming parser that uses an
`args.Iterator` to provide it with arguments lazily.
```zig
const std = @import("std");
const clap = @import("clap");
const debug = std.debug;
pub fn main() !void {
const allocator = std.heap.direct_allocator;
// First we specify what parameters our program can take.
const params = [_]clap.Param(u8){
clap.Param(u8){
.id = 'h',
.names = clap.Names{ .short = 'h', .long = "help" },
},
clap.Param(u8){
.id = 'n',
.names = clap.Names{ .short = 'n', .long = "number" },
.takes_value = true,
},
clap.Param(u8){
.id = 'f',
.takes_value = true,
},
};
// We then initialize an argument iterator. We will use the OsIterator as it nicely
// wraps iterating over arguments the most efficient way on each os.
var iter = try clap.args.OsIterator.init(allocator);
defer iter.deinit();
// Initialize our streaming parser.
var parser = clap.StreamingClap(u8, clap.args.OsIterator){
.params = params,
.iter = &iter,
};
// Because we use a streaming parser, we have to consume each argument parsed individually.
while (try parser.next()) |arg| {
// arg.param will point to the parameter which matched the argument.
switch (arg.param.id) {
'h' => debug.warn("Help!\n"),
'n' => debug.warn("--number = {}\n", arg.value.?),
// arg.value == null, if arg.param.takes_value == false.
// Otherwise, arg.value is the value passed with the argument, such as "-a=10"
// or "-a 10".
'f' => debug.warn("{}\n", arg.value.?),
else => unreachable,
}
}
}
```
### `ComptimeClap`
The `ComptimeClap` is a wrapper for `StreamingClap`, which parses all the arguments and makes
them available through three functions (`flag`, `option`, `positionals`).
```zig
const std = @import("std");
const clap = @import("clap");
const debug = std.debug;
pub fn main() !void {
const allocator = std.heap.direct_allocator;
// First we specify what parameters our program can take.
// We can use `parseParam` to parse a string to a `Param(Help)`
const params = comptime [_]clap.Param(clap.Help){
clap.parseParam("-h, --help Display this help and exit. ") catch unreachable,
clap.parseParam("-n, --number <NUM> An option parameter, which takes a value.") catch unreachable,
clap.Param(clap.Help){
.takes_value = true,
},
};
// We then initialize an argument iterator. We will use the OsIterator as it nicely
// wraps iterating over arguments the most efficient way on each os.
var iter = try clap.args.OsIterator.init(allocator);
defer iter.deinit();
// Parse the arguments
var args = try clap.ComptimeClap(clap.Help, params).parse(allocator, clap.args.OsIterator, &iter);
defer args.deinit();
if (args.flag("--help"))
debug.warn("--help\n");
if (args.option("--number")) |n|
debug.warn("--number = {}\n", n);
for (args.positionals()) |pos|
debug.warn("{}\n", pos);
}
```
The data structure returned from this parser has lookup speed on par with array access (`arr[i]`)
and validates that the strings you pass to `option` and `flag` are actually parameters that the
program can take:
```zig
const std = @import("std");
const clap = @import("clap");
pub fn main() !void {
const allocator = std.heap.direct_allocator;
const params = [_]clap.Param(void){clap.Param(void){
.names = clap.Names{ .short = 'h', .long = "help" },
}};
var iter = clap.args.OsIterator.init(allocator);
defer iter.deinit();
const exe = try iter.next();
var args = try clap.ComptimeClap(void, params).parse(allocator, clap.args.OsIterator, &iter);
defer args.deinit();
_ = args.flag("--helps");
}
```
```
zig-clap/src/comptime.zig:109:17: error: --helps is not a parameter.
@compileError(name ++ " is not a parameter.");
^
zig-clap/src/comptime.zig:77:45: note: called from here
const param = comptime findParam(name);
^
zig-clap/example/comptime-clap-error.zig:18:18: note: called from here
_ = args.flag("--helps");
^
```
Ofc, this limits you to parameters that are comptime known.
### `help`
The `help`, `helpEx` and `helpFull` are functions for printing a simple list of all parameters the
program can take.
```zig
const std = @import("std");
const clap = @import("clap");
pub fn main() !void {
const stderr_file = try std.io.getStdErr();
var stderr_out_stream = stderr_file.outStream();
const stderr = &stderr_out_stream.stream;
// clap.help is a function that can print a simple help message, given a
// slice of Param(Help). There is also a helpEx, which can print a
// help message for any Param, but it is more verbose to call.
try clap.help(
stderr,
comptime [_]clap.Param(clap.Help){
clap.parseParam("-h, --help Display this help and exit. ") catch unreachable,
clap.parseParam("-v, --version Output version information and exit.") catch unreachable,
},
);
}
```
```
-h, --help Display this help and exit.
-v, --version Output version information and exit.
```
The `help` functions are the simplest to call. It only takes an `OutStream` and a slice of
`Param(Help)`.
The `helpEx` is the generic version of `help`. It can print a help message for any
`Param` give that the caller provides functions for getting the help and value strings.
The `helpFull` is even more generic, allowing the functions that get the help and value strings
to return errors and take a context as a parameter.
|
