getargs

An argument parser that is truly zero-cost, similar to Unix's getopts.

About

getargs is a low-level, efficient and versatile argument parser that works similarly to getopts. It works by producing a stream of options, and after each option, your code decides whether to require and retrieve the value for the option or not.

You don't have to declare a list of valid options up-front, so getargs does not have to allocate space for them or spend runtime searching for them. This also means that you have to write your own help message, but since --help is just another flag, there are no restrictions on what you do with it.

Features

• Short -f and long --flag flags
• Required implicit values -i VALUE and --implicit VALUE
• Required or optional explicit values -eVALUE and --explicit=VALUE
• Positional arguments and --
• Parse options at the beginning of the argument list, or anywhere

Benefits

• Zero cost
• Zero copy
• Zero unsafe code
• Zero dependencies
• Zero allocation
• Simple to use yet versatile
• #![no_std]-compatible
• Compatible with &str and &[u8]

Performance

getargs has had a lot of attention put into profiling and optimization, and on a modern machine it takes under 0.2μs to parse a short array of 12 arguments.

In our testing, getargs is faster than every other argument parsing library on crates.io. Its closest competitor is gumdrop, which is only ~30% slower in the worst case, and its second-closest competitor is getopt, which takes three times as long. Other libraries degrade quickly; clap takes 45x longer. (This is not an entirely fair comparison though, as clap is not just an argument-parsing library, but an entire command-line application framework. It is perhaps overqualified for simple tasks.)

Example

For examples, see [the examples directory][./examples/] for small programs that you can compile and run yourself to see how getargs works.

License

MIT.