# MOROS Shell
## Configuration
The shell will read `/ini/shell.sh` during initialization to setup its
configuration.
## Commands
The main commands have a long name, a one-letter alias, and may have
additional common aliases.
**Alias** command:
> alias d delete
**Delete** file:
> d a.txt
> delete a.txt
**Copy** file:
> c a.txt b.txt
> copy a.txt b.txt
**Move** file:
> m a.txt b.txt
> move a.txt b.txt
**Print** string:
> p "Hi"
> print "Hi"
**Read** file:
> r a.txt
> read a.txt
**Write** file:
> w a.txt
> write a.txt
**Write** dir:
> write /usr/alice/ # with a trailing slash to create a dir instead of a file
**List** files in dir:
> list /usr/alice
When executed without arguments, this command will list the files of the
current directory.
**Goto** dir:
> goto /usr/alice
When executed without arguments, this command will print the current directory.
## Combiners (TODO)
**And combiner:**
> read foo.txt and read bar.txt
**Or combiners:**
> read foo.txt or read bar.txt
## Pipes and Redirections (WIP)
A thin arrow `->` can be used for piping the output from one command to the
input of another command (TODO):
> read foo.txt -> write bar.txt
A fat arrow `=>` can be used for redirecting directly to a file:
> read foo.txt => bar.txt
In the following example the standard output is redirected to the null device
file while the standard error is kept:
> time read foo.txt => /dev/null
The standard output is implied as the source of a redirection, but it is
possible to explicitly redirect a handle to another (TODO):
> time read foo.txt [1]=>[3]
Or to redirect a handle to a file:
> time read foo.txt [1]=> bar.txt
Or to pipe a handle to another command:
> time read foo.txt [1]-> write bar.txt
It is possible to chain multiple redirections:
> time read foo.txt [1]=> bar.txt [2]=> time.txt
When the arrow point to the other direction the source and destination are
swapped and the standard input is implied:
> http <= req.txt => res.txt
Here we redirect `req.txt` to `stdin` and `stdout` to `res.txt`. If both files
are the same we can use this shortcut:
> http <=> tmp.txt
Redirections should be declared before piping (TODO):
> write <= req.txt => /net/http/moros.cc -> find --line href -> sort
NOTE: The following handles are available when a process is created:
- `stdin(0)`
- `stdout(1)`
- `stderr(2)`
- `stdnull(3)`
A redirection with a single arrow head will truncate its destination while
multiple heads like `=>>` will append to it.
NOTE: Arrows can be longer, and also shorter in the case of fat arrows:
> read foo.txt --> write bar.txt
> read foo.txt -> write bar.txt
> read foo.txt ==> bar.txt
> read foo.txt => bar.txt
> read foo.txt > bar.txt
> write bar.txt <== foo.txt
> write bar.txt <= foo.txt
> write bar.txt < foo.txt
> read foo.txt ==>> bar.txt
> read foo.txt =>> bar.txt
> read foo.txt >> bar.txt
## Variables
- Name of the shell or the script: `$0`
- Script arguments: `$1`, `$2`, `$3`, `$4`, ...
- Exit code: `$?`
- Process environment variable: `$HOME`, ...
- Shell environment variable: `$foo`, ...
Setting a variable in the shell environment is done with the following command:
> set foo 42
> set bar "Alice and Bob"
And accessing a variable is done with the `$` operator:
> print $foo
42
> print "Hello $bar"
Hello Alice and Bob
The process environment is copied to the shell environment when a session is
started. By convention a process env var should be in uppercase and a shell
env var should be lowercase.
Unsetting a variable is done like this:
> unset foo
## Globbing
MOROS Shell support filename expansion or globbing for `*` and `?` wildcard
characters, where a pattern given in an argument of a command will be replaced
by files matching the pattern.
- `*` means zero or more chars except `/`
- `?` means any char except `/`
For example `/tmp/*.txt` will match any files with the `txt` extension inside
`/tmp`, and `a?c.txt` will match a file named `abc.txt`.
## Tilde Expansion
The tilde character `~` is a shortcut to `$HOME` so `~/test` will be expanded
to `$HOME/test` by the shell.