1 1 4 Shell Builtin Commands 1 ************************ 1
1 · Bourne Shell Builtins Builtin commands inherited from the Bourne 1 Shell. · Bash Builtins Table of builtins specific to Bash. · Modifying Shell Behavior Builtins to modify shell attributes and 1 optional behavior. · Special Builtins Builtin commands classified specially by 1 POSIX. 1 1 Builtin commands are contained within the shell itself. When the name 1 of a builtin command is used as the first word of a simple command 1 (⇒Simple Commands), the shell executes the command directly, 1 without invoking another program. Builtin commands are necessary to 1 implement functionality impossible or inconvenient to obtain with 1 separate utilities. 1 1 This section briefly describes the builtins which Bash inherits from 1 the Bourne Shell, as well as the builtin commands which are unique to or 1 have been extended in Bash. 1 1 Several builtin commands are described in other chapters: builtin 1 commands which provide the Bash interface to the job control facilities DONTPRINTYET 1 (⇒Job Control Builtins), the directory stack (*noteDirectory 1DONTPRINTYET 1 (⇒Job Control Builtins), the directory stack (⇒Directory Stack Builtins), the command history (⇒Bash History Builtins), 11 and the programmable completion facilities (⇒Programmable Completion Builtins). 1 1 Many of the builtins have been extended by POSIX or Bash. 1 1 Unless otherwise noted, each builtin command documented as accepting 1 options preceded by '-' accepts '--' to signify the end of the options. 1 The ':', 'true', 'false', and 'test' builtins do not accept options and 1 do not treat '--' specially. The 'exit', 'logout', 'return', 'break', 1 'continue', 'let', and 'shift' builtins accept and process arguments 1 beginning with '-' without requiring '--'. Other builtins that accept 1 arguments but are not specified as accepting options interpret arguments 1 beginning with '-' as invalid options and require '--' to prevent this 1 interpretation. 1