estack.eclass

Name

estack.eclass -- stack-like value storage support

Description

Support for storing values on stack-like variables.

Functions

estack_push <stack> [items to push]

Push any number of items onto the specified stack. Pick a name that is a valid variable (i.e. stick to alphanumerics), and push as many items as you like onto the stack at once.

The following code snippet will echo 5, then 4, then 3, then ...

estack_push mystack 1 2 3 4 5
while estack_pop mystack i ; do
        echo "${i}"
done

estack_pop <stack> [variable]

Pop a single item off the specified stack. If a variable is specified, the popped item is stored there. If no more items are available, return 1, else return 0. See estack_push for more info.

evar_push <variable to save> [more vars to save]

This let's you temporarily modify a variable and then restore it (including set vs unset semantics). Arrays are not supported at this time.

This is meant for variables where using local does not work (such as exported variables, or only temporarily changing things in a func).

For example:

evar_push LC_ALL
export LC_ALL=C
... do some stuff that needs LC_ALL=C set ...
evar_pop

# You can also save/restore more than one var at a time
evar_push BUTTERFLY IN THE SKY
... do stuff with the vars ...
evar_pop     # This restores just one var, SKY
... do more stuff ...
evar_pop 3   # This pops the remaining 3 vars

evar_push_set <variable to save> [new value to store]

This is a handy shortcut to save and temporarily set a variable. If a value is not specified, the var will be unset.

evar_pop [number of vars to restore]

Restore the variables to the state saved with the corresponding evar_push call. See that function for more details.

eshopts_push [options to `set` or `shopt`]

Often times code will want to enable a shell option to change code behavior. Since changing shell options can easily break other pieces of code (which assume the default state), eshopts_push is used to (1) push the current shell options onto a stack and (2) pass the specified arguments to set.

If the first argument is -s or -u, we assume you want to call shopt rather than set as there are some options only available via that.

A common example is to disable shell globbing so that special meaning/care may be used with variables/arguments to custom functions. That would be:

eshopts_push -o noglob
for x in ${foo} ; do
        if ...some check... ; then
                eshopts_pop
                return 0
        fi
done
eshopts_pop

eshopts_pop

Restore the shell options to the state saved with the corresponding eshopts_push call. See that function for more details.

eumask_push <new umask>

Set the umask to the new value specified while saving the previous value onto a stack. Useful for temporarily changing the umask.

eumask_pop

Restore the previous umask state.

Maintainers

base-system@gentoo.org

Reporting Bugs

Please report bugs via https://bugs.gentoo.org/