Function hostname 

pub fn hostname() -> Result<String>

Get the host device’s hostname.

Usually hostnames are case-insensitive, but it’s not a hard requirement.

Platform-Specific Character Limitations

Unix/Linux/BSD

• Maximum length: 255 bytes (excluding null terminator)
• Encoding: Must be valid UTF-8
• Characters: Typically follows RFC 952/1123 DNS hostname rules:
  • Alphanumeric characters (a-z, A-Z, 0-9)
  • Hyphens (-), but not at start or end
• Note: POSIX allows any character except null and newline, but network hostnames should follow DNS rules for interoperability

Windows

• Maximum length: 63 characters for DNS hostname (per label)
• Encoding: UTF-16 (converted to UTF-8 String)
• Characters: Follows DNS hostname rules (RFC 1123):
  • Alphanumeric characters (a-z, A-Z, 0-9)
  • Hyphens (-), but not at start or end

Redox

• Reads from /etc/hostname file
• First line of file is used as hostname
• No inherent character limitations beyond file system

Web (WASM)

• Returns the document’s domain name
• Follows DNS hostname rules as enforced by browsers
• Must be valid UTF-8

Other Platforms

• WASI: Returns system hostname or defaults to “localhost”
• Default: Returns “localhost” for unsupported platforms

Notes

For maximum compatibility across all platforms and network protocols, hostnames should:

• Be 63 characters or less
• Contain only ASCII alphanumeric characters and hyphens
• Not start or end with a hyphen
• Be case-insensitive (though case may be preserved)