1.10. Command Interpreters

Two command line interfaces:

• Simple (old) command interpreter:
  • sequential statements
  • statements separated by newline or ';'
  • no conditional execution except simple builtin rules:
    • "run cmd1; run cmd2; run cmd3"
      will always run all three commands
    • "run cmd1 cmd2 cmd3"
      will stop when a command fails
  • "scripts" (canned sequences of commands) avaialble using "autoscr" command
    
    
• Hush Shell (from Busybox, see http://www.busybox.net/):
  • Bourne Shell compatible
  • (local) shell variables ("name=val"), (global) environment variables ("setenv name val")
  • Conditionals: "if ... then ... else ... fi"
  • Control loops: "for ... do ... done", "while ... do done", "until ... do ... done"
  • Control operators: && and || (AND and OR lists: "command1 && command2")
  • real shell scripts
    
    
  • no functions
  • no command substitution
  • no backquotes