# 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)