The Datafile PD-CD 4/DATAFILE_PDCD4.iso/unix/riscbsd/datafile/usd/03_shell/t4_txt

Text File | 1996-10-12 | 2.8 KB | 397 lines

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Appendix A - Grammar






























































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     item:          word
               input-output
               name = value

     simple-command: item
               simple-command item

     command:  simple-command
               ( command-list )
               { command-list }
               for name do command-list done
               for name in word  do command-list done
               while command-list do command-list done
               until command-list do command-list done
               case word in case-part  esac
               if command-list then command-list else-part fi

     pipeline:      command
               pipeline  command

     andor:         pipeline
               andor && pipeline
               andor  pipeline

     command-list:  andor
               command-list ;
               command-list &
               command-list ; andor
               command-list & andor

     input-output:  > file
               < file
                word
                word

     file:          word
               & digit
               & -

     case-part:     pattern ) command-list ;;

     pattern:       word
               pattern  word

     else-part:     elif command-list then command-list else-part
               else command-list
               empty

     empty:

     word:          a sequence of non-blank characters

     name:          a sequence of letters, digits or underscores starting with a letter










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     digit:         0 1 2 3 4 5 6 7 8 9






























































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Appendix B - Meta-characters and Reserved Words

a) syntactic

           pipe symbol

     &&    `andf' symbol

           `orf' symbol

     ;     command separator

     ;;    case delimiter

     &     background commands

     ( )   command grouping

     <     input redirection

           input from a here document

     >     output creation

           output append



b) patterns

           match any character(s) including none

     ?     match any single character

     [...] match any of the enclosed characters



c) substitution

     ${...}
           substitute shell variable

     `...` substitute command output



d) quoting

     \     quote the next character

     '...' quote the enclosed characters except for '











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     "..." quote the enclosed characters except for $ ` \ "



e) reserved words

     if then else elif fi
     case in esac
     for while until do done
     {  }