3.8 Shell Scripts 32 4 Shell Builtin Commands 33 4.1 Bourne Shell Builtins 33 4.2 Bash Builtin Commands 39 4.3 The Set Builtin 50 4.4 Special Builtins 54 5 Shell Variables 55 5.1 Bourne Shell Variables 55 5.2 Bash Variables 55 6 Bash Features 65 6.1 Invoking Bash 65 6.2 Bash Start