Siac is a commandline client which interacts with the sia daemon. It can instruct the sia daemon to perform task like upload/download of files or send sia coins to an address. The full set of capabillities can be found using the help function built into siac. Each subcommand also has help strings.

Siac comes bundled in the “Sia Daemon” package. See http://sia.tech/apps/

 >siac help  
 
 Sia Client v1.1.1
Usage:
  siac [flags]
  siac [command]
Available Commands:
   consensus   Print the current state of consensus
   gateway     Perform gateway actions
   host        Perform host actions
   ...


>siac consensus help

Usage:
siac consensus [flags]
Global Flags:
  -a, --addr string   which host/port to communicate ...

Siac is the tool most frequently used by developers when interacting with Sia. For most uses, siac provides more complete functionality and gets new features sooner compared to the graphical client.

Siac operates entirely through the Sia API. A third party app can easily replicate all functionality in siac simply by talking to Sia's HTTP API.