mrsh status

http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html

- [x] Parser
- [x] Basic line parser
- [x] Comments
- [x] Quoting, escaping
- [x] Aliases
- [x] Parameters, variables
- [x] Word expansions
- [x] Parameter expansion
- [x] Variables
- [x] Expressions
- [x] Command substitution
- [x] `` `…` ``
- [x] `$(…)`
- [x] Arithmetic expansion
- [x] Redirections
- [x] Redirecting IO
- [x] Here-document
- [x] Pipelines
- [x] Async lists
- [x] Compound commands
- [x] `{…}`
- [x] `(…)`
- [x] Control structures
- [x] `if`, `elif`, `else`, `fi`
- [x] `while`, `for`, `until`, `do`, `done`
- [x] `case`, `in`, `esac`
- [x] Function definition
- [ ] Shell
- [x] Simple commands
- [x] Redirections
- [x] Redirecting IO
- [x] Here-document
- [x] Pipelines
- [x] and-or lists
- [x] Async lists
- [x] Compound commands
- [x] `{…}`
- [x] `(…)`
- [x] Parameters, variables
- [x] Shell variables
- [x] Positional parameters, special parameters
- [x] Word expansions
- [x] Tilde expansion
- [x] Parameter expansion
- [x] Variables
- [x] Expressions
- [x] Command substitution
- [x] Arithmetic expansion
- [x] Field splitting
- [x] Pathname expansion
- [x] Quote removal
- [x] Control structures
- [x] Conditions
- [x] Loops
- [x] Case
- [x] Aliases
- [x] Function definition
- [x] CLI flags
- [x] Job control
- [ ] Exit status and errors
- [x] Signals and error handling
- [x] Pattern matching
- [x] POSIX build system
- [x] Special builtins
- [x] `break`
- [x] `:` (colon)
- [x] `continue`
- [x] `.` (dot)
- [x] `eval`
- [x] `exec`
- [x] `exit`
- [x] `export`
- [x] `readonly`
- [x] `return`
- [x] `set`
- [x] `shift`
- [x] `times`
- [x] `trap`
- [x] `unset`
- [x] Regular builtins
- [x] `type`
- [x] `ulimit`
- [x] `alias`
- [x] `bg`
- [x] `cd`
- [x] `command`
- [x] `false`
- [x] `fg`
- [x] `getopts`
- [x] `hash`
- [x] `jobs`
- [x] `pwd`
- [x] `read`
- [x] `true`
- [x] `umask`
- [x] `unalias`
- [x] `wait`