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 IEEE Std 1003.1-2001,  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
       IEEE Std 1003.1-2001 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.

SEE ALSO

       Special Built-In Utilities

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition,
       Standard  for  Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers,
       Inc  and  The  Open Group. In the event of any discrepancy between this version and the original IEEE and
       The Open Group Standard, the original IEEE and The Open Group  Standard  is  the  referee  document.  The
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .