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Re: Can not declare a local variable if an global ro-variable exists wit
Re: Can not declare a local variable if an global ro-variable exists with the same name
Fri, 29 Mar 2019 08:45:02 -0400
On Wed, Mar 27, 2019 at 02:06:51PM +0100, address@hidden wrote:
> If I declare a global read-only variable and I try to declare a local
> variable with that name, I can not create
> the local variable.
> I expect that local variables can be declared independently for the
> global variables.
The purpose of the readonly flag on shell variables is to support the
restricted shell. I will pause while you laugh and/or cry.
In order for a restricted shell to have half a chance of working (keeping
the user imprisoned), the PATH variable has to be immutable. If the
user can modify PATH, they can run a real shell and escape.
So, in rbash and friends, PATH gets marked readonly, and bash treats
the readonly flag as sacrosanct. Allowing a user to work around it
simply by creating a function would let them break out of the restricted
shell too easily.
Readonly is forever.