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  • Shell Arithmetic
    IoT 과정 2017. 7. 6. 11:06
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    Creating Inter Variables

    number=123.45  // type : local string
    integer counter=12 // type : local integer
    typeset -i total=32767
    exort total // type : export integer
    integer minimum=-2147483648 // type : local integer


    Base10 and Others

    typeset -i int_num=10    //value string: 10
    typeset -i2 bin_num=10  //value string: 2#1010
    typeset -i8 oct_num=10  //value string: 8#12
    typeset -i16 hex_num=10  //value string: 16#a


    Working with Arithmetic

    let x=4+5 // ((x=4+5))
    let "x= 4 + 5" // (( x = 4 + 5 ))
    print $((x=4+5))  --> 9
    print $x ---> 9


    Binary Operators 

    <<   shift bits left   (( 8 << 1 ))  --> 16  // 1000   10000
    >>   shift bits right (( 8 >> 1 )) -->  4  //   1000   100
    &     bitwise AND  (( a & b )) ---> // 1000 & 0100   = 0000
    |       bitwise OR    (( a | b ))  ----> // 1000 & 0110  = 1110  
    ^     bitwise exclusive OR  (( a^b )) ----> // 1000 & 1110 = 0110


    Working with Numeric Data

    awk    : UNIX command/program language
    bc      : Desktop calculator  
    expr   : Expression command with functions
    $(#string) : Length of string variable contents
    PPID : Integer number of parents process
    RANDOM : Random integer
    SECONDS : Elapsed secons




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