Korn Shell: Unix and Linux Programming Manual, Third Edition, The

Command Syntax

The shell begins parsing its input by breaking it into words. Words, which are sequences of characters, are delimited by unquoted white-space characters (space, tab and newline) or meta-characters (<, >, |, ;, &, (and)). Aside from delimiting words, spaces and tabs are ignored, while newlines usually delimit commands. The metacharacters are used in building the following tokens: <, <&, <<, >, >&, >>, etc. are used to specify redirections (see Input/Output Redirection below); | is used to create pipelines; |& is used to create co-processes (see Co-Processes later in this appendix); ; is used to separate commands; & is used to create asynchronous pipelines; && and || are used to specify conditional execution; ;; is used in case ...