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readonly(1)

readonly(1)                      User Commands                     readonly(1)



NAME
       readonly  -  shell  built-in function to protect the value of the given
       variable from reassignment

SYNOPSIS
   sh
       readonly [name]...

   ksh88
       **readonly [name [= value]]...


       **readonly -p

   ksh
       ++readonly [-p] [name [= value]]...

DESCRIPTION
   sh
       The given names are marked readonly and the values of these  names  may
       not  be  changed by subsequent assignment. If no arguments are given, a
       list of all readonly names is printed.

   ksh88
       The given names are marked readonly and these names cannot  be  changed
       by subsequent assignment.


       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 formats 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 execu‐
       tion environment in which:

           1.     Variables  with  values  set 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
                  re-input to the shell.




       On this manual page, ksh88(1) commands that are preceded by one or  two
       ** (asterisks) are treated specially in the following ways:

           1.     Variable  assignment  lists  preceding the command remain in
                  effect when the command completes.


           2.     I/O redirections are processed after variable assignments.


           3.     Errors cause a script that contains them to abort.


           4.     Words, following a command preceded by ** that  are  in  the
                  format  of a variable assignment, are expanded with the same
                  rules as a variable assignment. This means that  tilde  sub‐
                  stitution  is  performed after the = sign and word splitting
                  and file name generation are not performed.



   ksh
       readonly sets the readonly attribute on each of the variables specified
       by  name  which  prevents their values from being changed. If =value is
       specified, the variable name is set to value  before  the  variable  is
       made readonly.


       If  no  names  are  specified then the names and values of all readonly
       variables are written to standard output.


       readonly is built-in to the shell as  a  declaration  command  so  that
       field  splitting  and pathname expansion are not performed on the argu‐
       ments. Tilde expansion occurs on value.

       -p    Causes the output to be in a form of readonly commands  that  can
             be  used  as  input  to the shell to re-create the current set of
             readonly variables.



       On this manual page, ksh(1) commands that are preceded by one or two  +
       symbols are treated specially in the following ways:

           1.     Variable  assignment  lists  preceding the command remain in
                  effect when the command completes.


           2.     I/O redirections are processed after variable assignments.


           3.     Errors cause a script that contains them to abort.


           4.     They are not valid function names.


           5.     Words, following a command preceded by ++ that  are  in  the
                  format  of a variable assignment, are expanded with the same
                  rules as a variable assignment. This means that  tilde  sub‐
                  stitution  is performed after the = sign and field splitting
                  and file name generation are not performed.



EXIT STATUS
   ksh
       The following exit values are returned:

       0     Successful completion.


       >0    An error occurred.


ATTRIBUTES
       See attributes(7) for descriptions of the following attributes:


       tab() box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i) ATTRIBUTE  TYPEAT‐
       TRIBUTE VALUE _ Availabilitysystem/core-os


SEE ALSO
       ksh(1), ksh88(1), sh(1), typeset(1), attributes(7)



Oracle Solaris 11.4               11 May 2021                      readonly(1)
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