clap/examples/10_default_values.md
Ed Page bfa02fd418 test: More thoroughly test examples
This ports our example testing over to [trycmd](https://docs.rs/) so
we can:
- More thoroughly test our examples
- Provide always-up-to-date example usage

The old way of testing automatically picked up examples.  This new way
requires we have a `.md` file that uses the example in some way.

Notes:
- Moved overall example description to the `.md` file
- I added cross-linking between related examples
- `14_groups` had a redundant paragraph (twice talked about "one and
  only one"
2021-11-23 13:13:41 -06:00

748 B

Using Arg::default_value, rather than Option::unwrap_or, gives clap more information it can use with our argument.

For example, let's look at the help:

$ 10_default_values --help
myapp 

does awesome things

USAGE:
    10_default_values[EXE] [OPTIONS] [INPUT]

ARGS:
    <INPUT>    The input file to use [default: input.txt]

OPTIONS:
    -c <CONFIG>        The config file to use
    -h, --help         Print help information

<INPUT>'s description says what the default is while -c's does not.

Otherwise, they'll work the same:

$ 10_default_values
The input file is: input.txt
The config file is: config.json
$ 10_default_values other.txt -c other.toml
The input file is: other.txt
The config file is: other.toml