# The readonly builtin command

## Synopsis

    readonly [-p] [-a] [-A] [-f] [NAME[=VALUE] ...]

## Description

The `readonly` builtin command is used to mark variables or functions as
read-only, which means unchangeable. This implies that it can\'t be
unset anymore. A `readonly` variable may not be redefined in child
scopes. A readonly global may not be redefined as a function local
variable. Simple command environment assignments may not reference
readonly variables.

### Options

  Option   Description
  -------- ------------------------------------------------------------------------------------------------------------------------
  `-a`     refer to normal arrays
  `-A`     refer to associative arrays
  `-f`     refer to functions
  `-p`     print all read-only variables or functions, `-a`, `-A` and `-f` can be used to filter. The output is reusable as input

An argument of `--` disables further option processing.

### Return status

  Status   Reason
  -------- --------------------------------
  0        no error
  !=0      invalid option
  !=0      invalid combination of options
  !=0      a given `NAME` is invalid

## Examples

## Portability considerations

-   in POSIX(r), only the `-p` option is specified

## See also

-   [declare](../../commands/builtin/declare.md)
-   [unset](../../commands/builtin/unset.md)