READONLY(P)						     POSIX Programmer's Manual						       READONLY(P)

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
", <name>, <value>

       if name is set, and

	      "readonly %s
", <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 behav-
       ior, 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 Technol-
       ogy -- 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 .

IEEE
/The Open Group						       2003							       READONLY(P)