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https://github.com/michaelmacinnis/oh

A new Unix shell.
https://github.com/michaelmacinnis/oh

command-line concurrent functional interpreter language scheme scripting-language shell unix

Last synced: 29 days ago
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A new Unix shell.

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# Oh, a new Unix shell



## Why oh?



Oh is a reimagining of the Unix shell.



Oh provides:



- A simplified set of evaluation and quoting rules;

- Rich return values that work with standard shell constructs;

- First-class channels, pipes, environments and functions;

- A list type (no word splitting);

- Support for modularity;

- Lexical scope;

- Exceptions;

- Kernel-style fexprs (allowing the definition of new language constructs); and

- A syntax that deviates as little as possible from established conventions;



Oh was motivated by the belief that many of the flaws in current Unix shells

are not inherent but rather historical. Design choices that are now clearly

unfortunate in retrospect have been carried forward in the name of backward

compatibility.



Oh's goal is a language that is not only more powerful and more regular but

one that respects the conventions established by the Unix shell over the last

half-century.



## Getting started



### Installing



The easiest way to try oh is to download a precompiled binary.



#### DragonFly BSD



[amd64](https://github.com/michaelmacinnis/oh/releases/download/v0.8.3/oh-v0.8.3-dragonfly-amd64)



#### FreeBSD



[386](https://github.com/michaelmacinnis/oh/releases/download/v0.8.3/oh-v0.8.3-freebsd-386), [amd64](https://github.com/michaelmacinnis/oh/releases/download/v0.8.3/oh-v0.8.3-freebsd-amd64), [arm](https://github.com/michaelmacinnis/oh/releases/download/v0.8.3/oh-v0.8.3-freebsd-arm), [arm64](https://github.com/michaelmacinnis/oh/releases/download/v0.8.3/oh-v0.8.3-freebsd-arm64), [riscv64](https://github.com/michaelmacinnis/oh/releases/download/v0.8.3/oh-v0.8.3-freebsd-riscv64)



#### illumos



[amd64](https://github.com/michaelmacinnis/oh/releases/download/v0.8.3/oh-v0.8.3-illumos-amd64)



#### Linux



[386](https://github.com/michaelmacinnis/oh/releases/download/v0.8.3/oh-v0.8.3-linux-386), [amd64](https://github.com/michaelmacinnis/oh/releases/download/v0.8.3/oh-v0.8.3-linux-amd64), [arm](https://github.com/michaelmacinnis/oh/releases/download/v0.8.3/oh-v0.8.3-linux-arm), [arm64](https://github.com/michaelmacinnis/oh/releases/download/v0.8.3/oh-v0.8.3-linux-arm64), [mips](https://github.com/michaelmacinnis/oh/releases/download/v0.8.3/oh-v0.8.3-linux-mips), [mips64](https://github.com/michaelmacinnis/oh/releases/download/v0.8.3/oh-v0.8.3-linux-mips64), [mips64le](https://github.com/michaelmacinnis/oh/releases/download/v0.8.3/oh-v0.8.3-linux-mips64le), [mipsle](https://github.com/michaelmacinnis/oh/releases/download/v0.8.3/oh-v0.8.3-linux-mipsle), [ppc64](https://github.com/michaelmacinnis/oh/releases/download/v0.8.3/oh-v0.8.3-linux-ppc64), [ppc64le](https://github.com/michaelmacinnis/oh/releases/download/v0.8.3/oh-v0.8.3-linux-ppc64le), [riscv64](https://github.com/michaelmacinnis/oh/releases/download/v0.8.3/oh-v0.8.3-linux-riscv64), [s390x](https://github.com/michaelmacinnis/oh/releases/download/v0.8.3/oh-v0.8.3-linux-s390x)



#### macOS



[amd64](https://github.com/michaelmacinnis/oh/releases/download/v0.8.3/oh-v0.8.3-darwin-amd64), [arm64](https://github.com/michaelmacinnis/oh/releases/download/v0.8.3/oh-v0.8.3-darwin-arm64)



#### OpenBSD



[386](https://github.com/michaelmacinnis/oh/releases/download/v0.8.3/oh-v0.8.3-openbsd-386), [amd64](https://github.com/michaelmacinnis/oh/releases/download/v0.8.3/oh-v0.8.3-openbsd-amd64), [arm](https://github.com/michaelmacinnis/oh/releases/download/v0.8.3/oh-v0.8.3-openbsd-arm), [arm64](https://github.com/michaelmacinnis/oh/releases/download/v0.8.3/oh-v0.8.3-openbsd-arm64)



#### Solaris



[amd64](https://github.com/michaelmacinnis/oh/releases/download/v0.8.3/oh-v0.8.3-solaris-amd64)



You can also build oh from source. With Go 1.21 or later installed, type,



    go install github.com/michaelmacinnis/[email protected]



### Configuring



When oh starts, it attempts to read a file called `.oh-rc` in the home

directory of the current user. You can override this path by setting

the OH_RC environment variable to the full path of an alternative file

before invoking oh.



The oh rc file is useful for setting environment variables and defining

custom commands. It's also a good place to override oh's default prompt.

The command below replaces oh's default prompt method with one that

displays the current date.



    replace-make-prompt (method (suffix) {

        return `(date)$suffix

    })



Oh (thanks to peterh/liner) also provides a searchable command history.

By default, this history is stored in a file called `.oh-history` in

your home directory. You can override this by setting the OH_HISTORY

environment variable to the full path of an alternative file before

invoking oh.



## Comparing oh to other Unix shells



Oh is a Unix shell. If you've used other Unix shells, oh should feel

familiar. Below are some specific differences you may encounter.



### Clobbering



When redirecting output oh will not overwrite an existing file. To force

oh to overwrite (clobber) an existing file add a pipe, `|`, character

immediately after the redirection operator. For example,



    command >| out.txt



Oh's pipe and redirection syntax is as follows.



| Syntax    | Redirection                        |

|----------:|:----------------------------------:|

|    `<`    | input-from                         |

|    `>`    | output-to                          |

|    `>&`   | output-errors-to                   |

|    `>&\|` | output-errors-clobbers             |

|    `>>`   | append-output-to                   |

|    `>>&`  | append-output-errors-to            |

|    `>\|`  | output-clobbers                    |

|    `\|`   | pipe-output-to                     |

|    `\|&`  | pipe-output-errors-to              |

|    `\|<`  | -named-pipe-input-from* |

|    `\|>`  | -named-pipe-output-to*  |



\* - Used in process substitution.



### Command substitution



Many Unix shells support command substitution using the historical

backtick syntax,



    `command`



or the POSIX syntax,



    $(command)



Oh has one syntax for command substitution,



    `(command)



This syntax is both nestable and unambiguous.



### Here documents



Oh does not have here documents. It does however allow strings to span

lines and provides a `here` command that takes a string argument and can

be used to the same effect. For example,



    # Build oh for supported BSD platforms

    here "

    dragonfly amd64

    freebsd 386

    freebsd amd64

    freebsd arm

    freebsd arm64

    openbsd 386

    openbsd amd64

    openbsd arm

    openbsd arm64

    openbsd mips64

    " | mill (o a) {

        echo ${o}/${a}

        GOOS=${o} GOARCH=${a} go build -o oh-latest-${o}-${a}

    }



### Variables



To introduce a new variable, use the `define` command,



    define x 3



To introduce a variable that will be visible to external processes,

use the `export` command,



    export GOROOT /usr/local/go



To set the value of an existing variable, use the `set` command,



    set x 4



### Variables and implicit concatenation



Like other shells, oh implicitly concatenates adjacent string/symbol

values. Unlike other shells, oh allows a larger set of characters to

appear in variable names. In addition to letters, numbers, and the

underscore character, the following characters,



    '!', '%', '*', '+', '-', '?', '[', ']',  and '^' 



can be used in oh variable names. The command,



    echo $set!



will cause oh to attempt to resolve a variable called `set!`. 

The following characters,



    ',', '.', '/', ':', '=', '@', and '~'



always result in a symbol of one character. This ensures that commands

like,



    cd $PWD/$dir



work as expected. When using implicit concatentation, unexpected behavior

can be avoided by enclosing variable names in braces.



### More detailed comparison



For a detailed comparison to other Unix shells see: [Comparing oh to other Unix Shells](https://htmlpreview.github.io/?https://raw.githubusercontent.com/michaelmacinnis/oh/master/doc/comparison.html)



## Using oh



For more information on using oh, see: [Using oh](doc/manual.md)



## Contributing to oh



Oh is an ongoing experiment and it needs your help. Try oh. Let me know

what works for you and what doesn't.



Pull requests are welcome. For information on contributing, see: [CONTRIBUTING](CONTRIBUTING.md)



You can also sponsor me through GitHub Sponsors or Patreon.



## License



[MIT](LICENSE)