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Same as declare but with local bindings for functions See bash using local Synonym for declare. May be used for compatibility with ksh or other POSIX complaint shell; however, set of option available may differ. In that case, it would be advantageous to declare attributes before or on assignment in a single statement assigning value to a variable.You may declare a variable without value to communicate that a variable may be modified from this point on or to unset a variable via assignment.Bitwise negation flips the bits in the binary representation of the numeric operand. The corresponding binary digits of both operands are multiplied to produce a result; for any given digit, the resulting digit is 1 if and only if the corresponding digit in both operands is also 1. A binary digit of the result is 1 if and only if the corresponding digits of the operands differ.
When used in a function, `declare' makes NAMEs local, as with the `local' command. Exit Status: Returns success unless an invalid option is supplied or a variable assignment error occurs.
# # declare an array and set key values # declare -a arr=(1) # arr=1 arr=$(( arr 1 )) echo $ # 1 echo $ # 2 for i in do arr[i]=$(( arr[i-1] arr[i-2] )) done echo $ # 199 declare -p arr ## expect #declare -a arr=(="1" ="3" ="4" ="7" ="11" ="18" ="29" ="47" ="76" ="123" ="199") option adds the associative array attribute to the variable name provided to the declare command.
An entire array can be assigned by enclosing the array items in parenthesis: is a relatively new addition to bash, it was not part of the original array implementation.
The following example shows some simple array usage (note the "[index]=value" assignment to assign a specific index): returns each item as a separate word.
For instance, let arguments will undergo globbing, pathname expansion, and word splitting unless you enclose the individual arguments in double quotes.
In the majority of situations, it's preferable to use double parentheses to evaluate arithmetic expressions.
(If this sounds a little convoluted, that's because it is.
See below for examples.) let evaluates each argument, arg, as a math expression. All numbers are represented internally as fixed-width integers.
Variables used in expressions have scope local to the command.
So, for instance, an argument to let will not be aware of other shell variables, unless they are exported.