Mini Shell

# Supported platforms

|  System | Support type | Supported versions | Notes |
|---|---|---|---|
| GNU/Linux | Tier 1 | Linux >= 2.6.32 with glibc >= 2.12 | |
| macOS | Tier 1 | macOS >= 10.7 | |
| Windows | Tier 1 | >= Windows 8 | VS 2015 and later are supported |
| FreeBSD | Tier 1 | >= 10 | |
| AIX | Tier 2 | >= 6 | Maintainers: @libuv/aix |
| IBM i | Tier 2 | >= IBM i 7.2 | Maintainers: @libuv/ibmi |
| z/OS | Tier 2 | >= V2R2 | Maintainers: @libuv/zos |
| Linux with musl | Tier 2 | musl >= 1.0 | |
| SmartOS | Tier 2 | >= 14.4 | Maintainers: @libuv/smartos |
| Android | Tier 3 | NDK >= r15b | |
| MinGW | Tier 3 | MinGW32 and MinGW-w64 | |
| SunOS | Tier 3 | Solaris 121 and later | |
| Other | Tier 3 | N/A | |

## Support types

* **Tier 1**: Officially supported and tested with CI. Any contributed patch
  MUST NOT break such systems. These are supported by @libuv/collaborators.

* **Tier 2**: Officially supported, but not necessarily tested with CI. These
  systems are maintained to the best of @libuv/collaborators ability,
  without being a top priority.

* **Tier 3**: Community maintained. These systems may inadvertently break and the
  community and interested parties are expected to help with the maintenance.

## Adding support for a new platform

**IMPORTANT**: Before attempting to add support for a new platform please open
an issue about it for discussion.

### Unix

I/O handling is abstracted by an internal `uv__io_t` handle. The new platform
will need to implement some of the functions, the prototypes are in
``src/unix/internal.h``.

If the new platform requires extra fields for any handle structure, create a
new include file in ``include/`` with the name ``uv-theplatform.h`` and add
the appropriate defines there.

All functionality related to the new platform must be implemented in its own
file inside ``src/unix/`` unless it's already done in a common file, in which
case adding an `ifdef` is fine.

Two build systems are supported: autotools and cmake. Ideally both need to be
supported, but if one of the two does not support the new platform it can be
left out.

### Windows

Windows is treated as a single platform, so adding support for a new platform
would mean adding support for a new version.

Compilation and runtime must succeed for the minimum supported version. If a
new API is to be used, it must be done optionally, only in supported versions.

### Common

Some common notes when adding support for new platforms:

* Generally libuv tries to avoid compile time checks. Do not add any to the
  autotools based build system or use version checking macros.
  Dynamically load functions and symbols if they are not supported by the
  minimum supported version.