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The declare builtin command

declare [-aAfFgilrtux] [-p] [NAME[=VALUE] ...]

# obsolete typeset synonym
typeset [-aAfFgilrtux] [-p] [NAME[=VALUE] ...]

declare is used to display or set variables along with variable attributes. When used to display variables/functions and their value, the output is re-usable as input for the shell.

If no NAME is given, it displays the values of all variables or functions when restricted by the -f option.

If NAME is followed by =VALUE, declare also sets the value for a variable.

When used in a function, declare makes NAMEs local variables, unless used with the -g option.

Don't use it's synonym typeset when coding for Bash, since it's tagged as obsolete.

Options

Below, [-+]X indicates an attribute, use -X to set the attribute, +X to remove it.

Option Description
[-+]a make NAMEs indexed arrays (removing with +a is valid syntax, but leads to an error message)
[-+]A make NAMEs associative arrays
-f restrict action or display to function names and definitions (removing with +f is valid syntax, but leads to an error message)
-F restrict display to function names only (plus line number and source file when debugging)
-g create global variables when used in a shell function; otherwise ignored (by default, declare declares local scope variables when used in shell functions)
[-+]i make NAMEs have the "integer" attribute
[-+]l convert NAMEs to lower case on assignment (makes sure the variable contains only lower case letters)
-p display the attributes and value of each NAME
[-+]r make NAMEs readonly (removing with +r is valid syntax, but not possible)
[-+]t make NAMEs have the "trace" attribute (effective only for functions)
[-+]u convert NAMEs to upper case on assignment (makes sure the variable contains only upper case letters)
[-+]x make NAMEs exported

Errors

Status Reason
0 no error
!= 0 invalid option
!= 0 invalid variable name given
!= 0 attempt to define a function using -f
!= 0 assignment to a readonly variable
!= 0 removing the readonly-attribute from a readonly variable
!= 0 assignment to an array variable without the compound assignment syntax (array=(…))
!= 0 attempt to use +a to "destroy" an array
!= 0 attemt to display a non-existent function with -f

Display defined functions

declare -f can be used to display all defined functions…

$ declare -f
foo () 
{ 
    echo "FOO is BAR"
}
world () 
{ 
    echo "Hello World!"
}
…or just a specific defined function.
$ declare -f foo
foo () 
{ 
    echo "FOO is BAR"
}

  • declare is not specified by POSIX®
  • there is a Bash synonym typeset, which is marked as obsolete: Use declare
  • the Korn shell typeset special command is not fully compatible, but some options are
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