Every utility / function needs to handle arguments. What usually happens is that every function does all the grunt work to parse `$argv` itself, and while some patterns do tend to recur, it's different almost every time. Enter fish `getopts`.
A string containing the option characters recognized by the utility calling `getopts`. If a `<letter>` or `<word>` ends in `:`, the option is expected to have an argument, which may be supplied separately or next to the option without spaces in the same string.
To indicate long options: `<letter>:<word>` and `<word>` are both valid option strings that will attempt to match `-<letter>` and `--<word>`.
To indicate _only_ short options, do not specify a `:<word>` after `<letter>`. For example, `a b` will match `-a` or `-b`.
To indicate optional arguments, use a `^` character after a `:` at the end of the option in the option string. For example `<letter>:^` and `<letter>:<word>:^` are both valid. Optional arguments should be supplied in the same string as the option and without spaces, e.g, `-<letter>value` will correctly assign `value` as the argument to the the option `<letter>`, but `-<letter>` value, will parse `value` as the next argument in `<ARGV>`.
To specify optional arguments using the option's long form, use a `=` character after the option: `--<word>=value`.
Use a `:` at the beginning of the option string to enable strict mode. If enabled, `getopts` will exit with a status __> 0__ if or when an unknown option is found. See [Diagnostics](#diagnostics).
#### `<ARGV>`
List of options and operands to parse. `getopts` prints any matched options as well as available argument separated by a \n to stdout and returns with a status of __0__ if there are still arguments; else returns with a status __> 0__ if the end of the options is reached or an error occurs. See [Diagnostics](#diagnostics).
#### Summary
| Option String | Argument | Short Style | Long Style |
`getopts` obtains options and their arguments from a list of parameters that, as indicated by <optionstring>, are single letters preceded by a `-` or words preceded by `--` and possibly followed by an argument value.
fish `getopts` follows the specifications described in the [Utility Syntax Guidelines](http://pubs.opengroup.org/onlinepubs/7908799/xbd/utilconv.html). The following is a summary of the features:
+ Short options; single letters preceded by `-`, and long options; words preceded by `--`, are both supported.
+ Single letters may be grouped. `-abc` → `-a -b -c`
+ Options required to take an argument can specify the argument either in the same string as the option or separated from the by a space. (1) `-a argument`, (2) `-aargument`
+ Options that can take an argument optionally shall specify the argument in the same string as the option argument if in short option style: `-aargument`, or separated by a `=` if in long form: `--long-form=argument`. If a blank space is used, the following argument will be treated independently.
+ Options can appear multiple times in the same argument list. `getopts` will print every match sequentally on each call, and should default to the short form of the option if available.
+ The option delimiter `:` and optional argument character `^` shall not be used as an option.
+ `getopts` will return the remaining operands when the end of the options is reached, i.e, a `--` argument that is not an option is found, or an argument that does not begin with `-` is found.
## Environment Variables
The following environment variables are used internally by `getopts`. These variables are erased from memory when the function returns 1.
+ `__getopts_argv`_Preprocessed copy of arguments._
+ `__getopts_index`_Index of the next argument to handle._
+ `__getopts_required`_List of options with required arguments._
+ `__getopts_optional`_List of options with optional arguments._
## <a name="diagnostics"></a>Diagnostics
Possible exit status values are:
+ __0__: An argument formed like an option was found. This causes getopts to print the option short-style and its argument if avaiable. If strict-mode is enabled setting the first character of the option to `:`, an unknown option will cause `getopts` to fail. See below.
+ __1__: The end of the options was reached. Remaining operands are also sent to stdout.
+ __2__: An option argument was missing.
+ __3__: An unknown option was found. Only if strict-mode is enabled.
## Examples
```fish
function my_utility
while set optarg (getopts "l:long x: o:optional:^" $argv)
