# Command Line Interface (CLI)

When math.js is installed globally using npm, its expression parser can be used
from the command line. To install math.js globally:

```bash
$ npm install -g mathjs
```

Normally, a global installation must be run with admin rights (precede the
command with `sudo`). After installation, the application `mathjs` is available
via the command line:

```bash
$ mathjs
> 12 / (2.3 + 0.7)
4
> 12.7 cm to inch
5 inch
> sin(45 deg) ^ 2
0.5
> 9 / 3 + 2i
3 + 2i
> det([-1, 2; 3, 1])
-7
```

The command line interface can be used to open a prompt, to execute a script,
or to pipe input and output streams:

```bash
$ mathjs                                 # Open a command prompt
$ mathjs script.txt                      # Run a script file, output to console
$ mathjs script1.txt script2.txt         # Run two script files
$ mathjs script.txt > results.txt        # Run a script file, output to file
$ cat script.txt | mathjs                # Run input stream, output to console
$ cat script.txt | mathjs > results.txt  # Run input stream, output to file
```

You can also use it to create LaTeX from or sanitize your expressions using the
`--tex` and `--string` options:

```bash
$ mathjs --tex
> 1/2
\frac{1}{2}
```

```bash
$ mathjs --string
> (1+1+1)
(1 + 1 + 1)
```

To change the parenthesis option use the `--parenthesis=` flag:

```bash
$ mathjs --string --parenthesis=auto
> (1+1+1)
1 + 1 + 1
```

```bash
$ mathjs --string --parenthesis=all
> (1+1+1)
(1 + 1) + 1
```

# Command line debugging (REPL)

The library also provides a REPL (Read Evaluate Print Loop) via `bin/repl.js` which
loads mathjs in a Node.js command line environment.
You can either start it directly (`./bin/repl.js`) or via node (`node bin/repl.js`).

You can exit using either [ctrl]-[C] or [ctrl]-[D].

```bash
$ ./bin/repl.js 
> math.parse('1+1')
{ op: '+',
  fn: 'add',
  args: 
   [ { value: '1', valueType: 'number' },
     { value: '1', valueType: 'number' } ] }
> 
```