4.7.2. Simple Unix Interface Design Patterns

(mostly from "The Art of Unix Programming", Eric S. Raymond)

• Filter
  • maybe most fundamental Unix pattern
  • reads on stdin, emits to stdout
  • examples: tail(1), grep(1), tr(1)
  • beware of UUOCA

• Source
  • no input, outputs on stdout
  • examples: ls(1), ps(1), uname(1), w(1)

• Sink
  • consumes from stdin, but doesn't output
  • examples: lpr(1), mail(1),

• Cantrip
  • no input, no output
  • just "does" something
  • examples: clear(1), touch(1)

• Compiler
  • no stdin no stdout
  • takes one or two file args
  • convert file 1 one and writes to file 2
  • examples: gcc(1), convert(1), gpg(1), gzip(1)