Mark one or more variables or functions as read-only.

      readonly [-apf] [name] ... 

   -a   Treat each name as an array variable.

   -p   Print a list of all readonly names (This is the default)

   -f   Mark shell functions corresponding to the names as read-only.

The given names are marked readonly and the values of these names can not be changed by subsequent assignment.

If the -f option is given, then functions corresponding to the names are so marked.

If no arguments are given, or if ‘-p’ is given, a list of all readonly names is printed.

The ‘-a’ option means to treat each name as an array variable.

An argument of ‘–‘ disables further option processing.

If a variable name is followed by =word, the value of the variable is set to word.

The return status is 0 unless an invalid option is encountered, one of the names is not a valid shell variable name, or -f is supplied with a name that is not a function.

This is a BASH shell builtin, to display your local syntax from the bash prompt type: help [r]eadonly

“The stupid neither forgive nor forget, the naive forgive and forget, the wise forgive but do not forget” ~ Thomas Szasz (The second sin)

Related linux commands:

chmod – Change access permissions
env – Display, set, or remove environment variables
export – Set an environment variable
function – Define Function Macros
hostname – Print or set system name
local – Create variables
printenv – Print environment variables
shift – Shift positional parameters
Equivalent PowerShell cmdlet: Set-Variable -option:ReadOnly

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