declare

Declare variables and give them attributes.

SYNTAX
      declare [-afFrxi] [-p] [name[=value]]

OPTIONS

      -a  Each name is an array variable.

      -f   Use function names only.

      -F   Inhibit the display of function definitions; 
           only the function name and attributes are printed. 
           (implies -f)

      -i   The variable is to be treated as an integer; 
           arithmetic evaluation is performed when the 
           variable is assigned a value.

      -p   Display the attributes and values of each name. 
           When `-p' is used, additional options are ignored.

      -r   Make names readonly. These names cannot then
           be assigned values by subsequent assignment statements 
           or unset.

      -x   Mark each name for export to subsequent commands
           via the environment.

If no names are given, then `declare' will display the values of variables instead.

Using + instead of - turns off the attribute instead.

When used in a function, declare makes each name local, as with the local command.

The typeset command is supplied for compatibility with the Korn shell; however, it has been deprecated in favor of the declare builtin command.

The return status is zero unless an invalid option is encountered, an attempt is made to define a function using `-f foo=bar', an attempt is made to assign a value to a readonly variable, an attempt is made to assign a value to an array variable without using the compound assignment syntax, one of the names is not a valid shell variable name, an attempt is made to turn off readonly status for a readonly variable, an attempt is made to turn off array status for an array variable, or an attempt is made to display a non-existent function with `-f'.

"My mother never saw the irony in calling me a son-of-a-bitch" ~ Jack Nicholson

Related:

alias - Create an alias
env - Display, set, or remove environment variables
echo - Display message on screen
export - Set an environment variable
hostname - Print or set system name
local - Create variables
printenv - Print environment variables
readonly - Mark variables/functions as readonly
shift - Shift positional parameters
Equivalent Windows command: SET - Display, set, or remove Windows environment variables