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1---

2navhome: /docs

3next: true

4sort: 5

5title: Shell (:dojo)

6---

8# Shell (`:dojo`)

10<div class="row">

11<div class="col-md-8">

13The `:dojo` is the place to quickly experiment with Urbit. On

14the surface the `:dojo` is just a Hoon REPL. On the inside, the

15`:dojo` is a system for operating on and transforming data in

16Urbit.

18</div>

19</div>

21## Quickstart

23Evaluate a hoon expression:

25 ~your-urbit:dojo> (add 2 2)

26 ~your-urbit:dojo> %+ add 2 2

28Tall form Hoon may require multiple lines:

30 ~your-urbit:dojo> %+ add

31 ~your-urbit:dojo< 2

32 ~your-urbit:dojo< 2

34Use `=var` to save a shell variable:

36 ~your-urbit:dojo> =foo (add 2 2)

38Use `=dir` to set the current working directory:

40 ~your-urbit:dojo> =dir %/web

42Generators (files in `/gen`) are run with `+`:

44 ~your-urbit:dojo> +hello 'world'

46Save output to a file in `%clay` with `*`:

48 ~your-urbit:dojo> *some/file/path/hoon 'hello world'

50Run system commands from `:hood`, like `reload`, using `|`:

52 ~your-urbit:dojo> |reload %eyre

55### Generators

57**`+cat`** - Similar to Unix `cat`. Accepts a path.

59 ~your-urbit:dojo> +cat %/web/md

60 ~your-urbit:dojo> +cat /~talsur-todres/home/2/web/notes/md

62**`+curl`** - Similar to Unix `curl`. Accepts a `tape`.

64 ~your-urbit:dojo> +curl "http://nyt.com"

66**`+hello`** - Just prints the argument. Accepts a `@ta`.

68 ~your-urbit:dojo> +hello 'mars'

70**`+ls`** - Similar to Unix `ls`. Accepts a path.

72 ~your-urbit:dojo> +ls %/web

73 ~your-urbit:dojo> +ls /~talsur-todres/home/2/web/notes

75**`+moon`** - Generate a random moon from a planet. No arguments.

77 ~your-urbit:dojo> +moon

79**`+solid`** - Compile the current state of the kernel and output a noun. Usually downloaded to a file in unix. No arguments.

81 ~your-urbit:dojo> .urbit/pill +solid

83**`+ticket`** - Generate a ticket for an Urbit plot. Takes an Urbit name (`@p`).

85 ~your-urbit:dojo> +ticket ~talsur-todres-your-urbit

87**`+tree`** - Generate a recursive directory listing. Takes a path.

89 ~your-urbit:dojo> +tree %/web

91### Hood

93The hood is the system daemon. See `gen/hood` and `app/hood`.

95**`|hi`** - Sends a direct message. Sort of like Unix `write`. Accepts an urbit name (`@p`) and a string (`cord`).

97 ~your-urbit:dojo> |hi ~doznec 'you there?'

99**`|link`** / **`|unlink`** - Link / unlink a remote app. Accepts an Urbit name and an app name.

100

101 ~your-urbit:dojo> |link ~talsur-todres %octo

102

103**`|mass`** - Prints the current memory usage of all the kernel modules. No arguments.

104

105 ~your-urbit:dojo> |mass

106

107**`|reload`** - Reloads a kernel module (vane) from source. Accepts any number of vane names.

108

109 ~your-urbit:dojo> |reload %clay %eyre

110

111**`|reset`** - Reloads `hoon.hoon` and all modules. No arguments.

112

113 ~your-urbit:dojo> |reset

114

115**`|start`** - Starts an app. Accepts an app name.

116

117 ~your-urbit:dojo> |start %curl

118

119## Manual

120

121<h3 class="first child">Sources and sinks</h3>

122

123A dojo command is either a source or a sink. A source is just something that can be printed to your console or the result of some computation. A sink is an *effect*: a change to the filesystem, a network message, a change to your environment, or typed message to an app.

124

125Sources can be chained together, but we can only produce one effect per command.

126

127### Sinks

128

129#### `=` - Set variable

130

131Set any envronment variable:

132

133 ~your-urbit:dojo> =foo 42

134 ~your-urbit:dojo> (add 2 foo)

135