https://github.com/elves/posixsh

Experimental POSIX shell implementation
https://github.com/elves/posixsh

Last synced: 2 months ago
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Experimental POSIX shell implementation

• Host: GitHub
• URL: https://github.com/elves/posixsh
• Owner: elves
• License: bsd-2-clause
• Created: 2018-02-20T02:02:47.000Z (almost 7 years ago)
• Default Branch: master
• Last Pushed: 2023-07-03T09:41:09.000Z (over 1 year ago)
• Last Synced: 2024-08-03T01:39:21.899Z (6 months ago)
• Language: Shell
• Size: 531 KB
• Stars: 7
• Watchers: 9
• Forks: 1
• Open Issues: 1
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
This is xiaq's experimental POSIX shell. If it works out, it will eventually

to be integrated into [Elvish](https://github.com/elves/elvish).

License is BSD 2-clause.

Files in `spec/oil` are derived from the

[Oil](https://github.com/oilshell/oil), licensed under Apache License 2.0. See

[spec/oil/LICENSE](spec/oil/LICENSE).

## Status and limitations

The majority of POSIX shell features are implemented.

The following features are currently missing:

* [ ] Closing FDs in redirections (`<&-`, 2.7.5, 2.7.6)

* [ ] Background jobs and related features

    * [ ] All of 2.9.3 "Async lists"

    * [ ] `$!`

    * [ ] `bg`

    * [ ] `fg`

    * [ ] `jobs`

    * [ ] `wait`

    * [ ] `set -o monitor` (`set -m`)

    * [ ] `set -o notify` (`set -n`)

* [ ] `set -o errexit` (`set -e`)

* [ ] `set -o noexec` (`set -n`)

* [ ] `exec`

* [ ] `getopts`

* [ ] `hash`

* [ ] `$LINENO` (2.5.3)

* [ ] Signal handling

    * [ ] All of 2.11 "Signals and error handling"

    * [ ] `trap`

* [ ] Interactive features

    * [ ] `$ENV` (2.5.3)

    * [ ] `$PS1` (2.5.3)

    * [ ] `$PS2` (2.5.3)

    * [ ] `$PS4` (2.5.3)

    * [ ] `fc`

    * [ ] `set -o ignoreeof`

    * [ ] `set -o nolog`.

Some implemented features are incomplete:

- In `<<-` heredocs, leading tabs in expansions are not stripped (2.7.4). Example:

  ```sh

  cat <<-EOF

    $(echo '

    bar')

  EOF

  ```

  This should print an empty line followed by a line of just `bar`, but

  currently this implementation has a tab before the `bar`.

- Argument of variable expansions may not contain whitespaces (2.6.2). Example:

  ```sh

  echo ${x=foo  bar}

  ```

  This should print `foo bar` (with one space) and assign `$x` to `foo  bar`

  (with two spaces). This implementation treats this as a syntax error now.

Since Go doesn't support `fork`, subshells are run in the same process, with

their own virtualized working directories and variables. This approach has some

inherent limitations:

- Some properties cannot be virtualized: `ulimit`, `umask` and `exec` (when

  implemented) will affect the entire process.

- Code that actually depends on subshells running in separate processes won't

  work correctly.

The following features are out of scope and will likely never be implemented:

- `set -h`.

- `kill` and `newgrp` - both are widely available as standalone commands.

- Internationalization/localization. This includes support for `$LANG`, `$LC_*`

  and `$NLSPATH`.