readonly(1)                                                     readonly(1)

NAME
     readonly - protect shell variables

SYNOPSIS
     readonly[ name]...

DESCRIPTION
     The shell built-in readonly marks the specified shell variables as
     read-only, i.e. protects them from being changed by reassignment in
     the current shell. An error message is issued if any such attempt is
     subsequently made.

     This protection only applies to the current shell. This means that the
     variable may be reassigned in a subshell or in a parent shell (i.e.
     when you terminate the current shell). Within the current shell, how-
     ever, it is not possible to undo this protection.

     If you invoke readonly without arguments, a list of all existing
     read-only variables in the current shell is written to standard out-
     put.

OPERANDS
     The Korn shell ksh supports additional options, and a value can be
     assigned to the readonly variables [see ksh(1)].

     name  Name of the shell variable to be marked as read-only (i.e. pro-
           tected). You have to assign a value to this variable before you
           call readonly.

           You can list any number of shell variables, separated by commas.

           name not specified:

           All shell variables protected in the current shell are written
           on the standard output in the following format:

           readonly name

           or for the Korn shell ksh:

           name = value

           or, if the -p option is set:

           readonly name = value

ERROR MESSAGE
     name: is read only

     This error message is issued when you try to assign a value to a pro-
     tected shell variable.




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readonly(1)                                                     readonly(1)

LOCALE
     The LCMESSAGES environment variable governs the language in which
     message texts are displayed. If LCMESSAGES is undefined or is defined
     as the null string, it defaults to the value of LANG. If LANG is like-
     wise undefined or null, the system acts as if it were not internation-
     alized.

     The LCALL environment variable governs the entire locale. LCALL
     takes precedence over all the other environment variables which affect
     internationalization.

EXAMPLES
     Marking the shell variable HOME as read-only in the current shell:

     $ readonly HOME
     $ readonly
     readonly HOME
     $ sh
     $ readonly
     $ CTRL-D
     $ readonly
     readonly HOME

     The HOME variable is not protected in the subshell.

NOTES
     Some differences in behavior may occur when using readonly, depending
     on which shell is being used. The possible differences are not
     described specifically.

SEE ALSO
     ksh(1), sh(1).






















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