установить атрибут readonly для переменных (set the readonly attribute for variables)
Пролог (Prolog)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
Имя (Name)
readonly — set the readonly attribute for variables
Синопсис (Synopsis)
readonly name[=word]...
readonly -p
Описание (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.1‐2017, 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.
Параметры (Options)
See the DESCRIPTION.
Операнды (Operands)
See the DESCRIPTION.
Стандартный ввод (Stdin)
Not used.
Входные файлы (Input files)
None.
Переменные окружения (Environment variables)
None.
Асинхронные события (Asynchronous events)
Default.
Стандартный вывод (Stdout)
See the DESCRIPTION.
Стандартный вывод сообщений (Stderr)
The standard error shall be used only for diagnostic messages.
Выходные файлы (Output files)
None.
Расширенное описание (Extended description)
None.
Статус выхода (Exit)
0 All name operands were successfully marked readonly.
>0 At least one name could not be marked readonly, or the -p
option was specified and an error occurred.
Последствия ошибок (Consequences of errors)
Default.
The following sections are informative.
Использование в приложениях (Application usage)
None.
Примеры (Examples)
readonly HOME PWD
Обоснование (Rationale)
Some historical shells preserve the readonly attribute across
separate invocations. This volume of POSIX.1‐2017 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(1p) 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.
Будущие направления (Future directions)
None.
Смотри также (See also)
Section 2.14, Special Built-In Utilities
The Base Definitions volume of POSIX.1‐2017, Section 12.2,
Utility Syntax Guidelines
