This is the command readonlyposix that can be run in the OnWorks free hosting provider using one of our multiple free online workstations such as Ubuntu Online, Fedora Online, Windows online emulator or MAC OS online emulator
PROGRAM:
NAME
readonly — set the readonly attribute for variables
SYNOPSIS
readonly name[=word]...
readonly −p
DESCRIPTION
The variables whose names are specified shall be given the readonly attribute. The values
of variables with the readonly attribute cannot be changed by subsequent assignment, nor
can those variables be unset by the unset utility. If the name of a variable is followed
by =word, then the value of that variable shall be set to word.
The readonly special built-in shall support the Base Definitions volume of POSIX.1‐2008,
Section 12.2, Utility Syntax Guidelines.
When −p is specified, readonly writes to the standard output the names and values of all
read-only variables, in the following format:
"readonly %s=%s\n", <name>, <value>
if name is set, and
"readonly %s\n", <name>
if name is unset.
The shell shall format the output, including the proper use of quoting, so that it is
suitable for reinput to the shell as commands that achieve the same value and readonly
attribute-setting results in a shell execution environment in which:
1. Variables with values at the time they were output do not have the readonly attribute
set.
2. Variables that were unset at the time they were output do not have a value at the time
at which the saved output is reinput to the shell.
When no arguments are given, the results are unspecified.
OPTIONS
See the DESCRIPTION.
OPERANDS
See the DESCRIPTION.
STDIN
Not used.
INPUT FILES
None.
ENVIRONMENT VARIABLES
None.
ASYNCHRONOUS EVENTS
Default.
STDOUT
See the DESCRIPTION.
STDERR
The standard error shall be used only for diagnostic messages.
OUTPUT FILES
None.
EXTENDED DESCRIPTION
None.
EXIT STATUS
Zero.
CONSEQUENCES OF ERRORS
Default.
The following sections are informative.
APPLICATION USAGE
None.
EXAMPLES
readonly HOME PWD
RATIONALE
Some historical shells preserve the readonly attribute across separate invocations. This
volume of POSIX.1‐2008 allows this behavior, but does not require it.
The −p option allows portable access to the values that can be saved and then later
restored using, for example, a dot script. Also see the RATIONALE for export for a
description of the no-argument and −p output cases and a related example.
Read-only functions were considered, but they were omitted as not being historical
practice or particularly useful. Furthermore, functions must not be read-only across
invocations to preclude ``spoofing'' (spoofing is the term for the practice of creating a
program that acts like a well-known utility with the intent of subverting the real intent
of the user) of administrative or security-relevant (or security-conscious) shell scripts.
FUTURE DIRECTIONS
None.
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