readonly(1) User Commands readonly(1)NAMEreadonly - shell built-in function to protect the value of the given
variable from reassignment
SYNOPSIS
sh
readonly [name]...
ksh
**readonly [name [= value]]...
**readonly -p
ksh93
++readonly [-p] [name [= value]]...
DESCRIPTION
sh
The given names are marked readonly and the values of the these names
may not be changed by subsequent assignment. If no arguments are given,
a list of all readonly names is printed.
ksh
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, ksh(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.
ksh93
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 recreate the current set of
readonly variables.
On this manual page, ksh93(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
ksh93
The following exit values are returned:
0 Successful completion.
>0 An error occurred.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Availability │SUNWcs │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOksh(1), ksh93(1), sh(1), typeset(1), attributes(5)SunOS 5.11 2 Nov 2007 readonly(1)
