# Idempotent unpacking **URL:** \ **Category:** Ansible Project\ **Tags:** ansible-project\ **Created:** [October 4, 2012, 12:04pm UTC](https://forum.ansible.com/t/idempotent-unpacking/11953 "2012-10-04T12:04:05Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![Michael\_DeHaan](https://avatars.discourse-cdn.com/v4/letter/m/c4cdca/32.png) [@Michael\_DeHaan](https://forum.ansible.com/u/Michael_DeHaan)\ **Post date:** [October 4, 2012, 12:04pm UTC](https://forum.ansible.com/t/idempotent-unpacking/11953/1 "2012-10-04T12:04:05Z")
Try this. Though you'll want 0.8 such that the boolean works as you would expect.       - action: get\_url ...         register: get\_url\_result       - action: command tar ...         only\_if: "${get\_url\_result.changed}" (Adding an easier alternative to the only\_if syntax is on the top of my list for 0.9) ---
**Author:** ![Chamberlain\_Darren](https://avatars.discourse-cdn.com/v4/letter/c/ee7513/32.png) [@Chamberlain\_Darren](https://forum.ansible.com/u/Chamberlain_Darren)\ **Post date:** [October 4, 2012, 2:00pm UTC](https://forum.ansible.com/t/idempotent-unpacking/11953/2 "2012-10-04T14:00:14Z")
Seems like this request could be grouped with the easy conditionals stuff earmarked for 0.9; there could be when\_file\_exists and when\_file\_not\_exists conditions (or possibly better names like creates) which would translate to:    only\_if: "True == os.path.isfile('/path/to/created/file')" In related news, Ben, you can use the above only\_if now. \* Michael DeHaan \ [2012/10/04 08:04]: ---
**Author:** ![Michael\_DeHaan](https://avatars.discourse-cdn.com/v4/letter/m/c4cdca/32.png) [@Michael\_DeHaan](https://forum.ansible.com/u/Michael_DeHaan)\ **Post date:** [October 4, 2012, 2:08pm UTC](https://forum.ansible.com/t/idempotent-unpacking/11953/3 "2012-10-04T14:08:41Z")
Not really. The easy conditional stuff is probably going to compile down to an only\_if, and not result in network tests. It will get as easy as this though: when: changed('variable\_name') and maybe even automagic registering of previous commands via a stack, like when: changed('previous') or maybe even when: changed('task\_name') ---
**Author:** ![Ben\_Hood](https://avatars.discourse-cdn.com/v4/letter/b/8c91f0/32.png) [@Ben\_Hood](https://forum.ansible.com/u/Ben_Hood)\ **Post date:** [November 22, 2012, 10:08pm UTC](https://forum.ansible.com/t/idempotent-unpacking/11953/4 "2012-11-22T22:08:53Z")
Michael, > Try this. Though you’ll want 0.8 such that the boolean works as you > would expect. > > - action: get\_url … > register: get\_url\_result > > - action: command tar … > only\_if: “${get\_url\_result.changed}” > > (Adding an easier alternative to the only\_if syntax is on the top of > my list for 0.9) Thanks for the heads up on this (and sorry about the very late reply to your post). I don’t suppose that this construct would work with my current factoring: - name: Fetch Remote Packages action: get\_url url=$s3/$item dest=/opt/$item with\_items: - $tarball1 - $tarball2 - $tarball3 tags: - download Would I need to break this up to register the boolean, or could I put it into the loop somehow? Cheers, Ben ---
**Author:** ![Daniel\_Hokka\_Zakriss](https://avatars.discourse-cdn.com/v4/letter/d/f05b48/32.png) [@Daniel\_Hokka\_Zakriss](https://forum.ansible.com/u/Daniel_Hokka_Zakriss)\ **Post date:** [November 22, 2012, 10:25pm UTC](https://forum.ansible.com/t/idempotent-unpacking/11953/5 "2012-11-22T22:25:02Z")
Ben Hood wrote: > Michael, > > > Try this. Though you'll want 0.8 such that the boolean works as you > > would expect. > > > >       - action: get\_url ... > >         register: get\_url\_result > > > >       - action: command tar ... > >         only\_if: "${get\_url\_result.changed}" > > > > (Adding an easier alternative to the only\_if syntax is on the top of > > my list for 0.9) > > Thanks for the heads up on this (and sorry about the very late reply to > your post). > > I don't suppose that this construct would work with my current factoring: > > - name: Fetch Remote Packages >   action: get\_url url=$s3/$item dest=/opt/$item >   with\_items: >     - $tarball1 >     - $tarball2 >     - $tarball3 >   tags: >     - download > > Would I need to break this up to register the boolean, or could I put it > into the loop somehow? Are you wanting to extract each tarball depending on whether or not that particular one has changed, or do you want to run it if any of them change? The former would likely be best implemented using a task include file containing your get\_url and unpacking command, and using with\_items on the include, e.g.   tasks:   - include: fetch-extract.yml url=$s3/$item name=$item     with\_items:     - $tarball1     - $tarball2 and in fetch-extract.yml:   - name: fetch file     action: get\_url url=$url dest=/opt/$name     register: fetch\_result   - name: extract file     action: command tar -xzf /opt/$name     when\_boolean: ${fetch\_result.changed} The latter would be easier, just add register: foo and use ${foo.changed}. It will be True if any of the items was changed, and False if they were all unchanged. Daniel ---
**Author:** ![Michael\_DeHaan](https://avatars.discourse-cdn.com/v4/letter/m/c4cdca/32.png) [@Michael\_DeHaan](https://forum.ansible.com/u/Michael_DeHaan)\ **Post date:** [November 22, 2012, 10:49pm UTC](https://forum.ansible.com/t/idempotent-unpacking/11953/6 "2012-11-22T22:49:24Z")
I do not see a register in your example but generally except for yum and apt combining with items and register would only store the last result – Michael ---
**Author:** ![Daniel\_Hokka\_Zakriss](https://avatars.discourse-cdn.com/v4/letter/d/f05b48/32.png) [@Daniel\_Hokka\_Zakriss](https://forum.ansible.com/u/Daniel_Hokka_Zakriss)\ **Post date:** [November 22, 2012, 10:57pm UTC](https://forum.ansible.com/t/idempotent-unpacking/11953/7 "2012-11-22T22:57:43Z")
Michael DeHaan wrote: > I do not see a register in your example but generally except for yum and > apt combining with items and register would only store the last result No, register: on a with\_items gets a dict with changed being the sum of all changed, and results being a list of the results for each item. Daniel ---
**Author:** ![Ben\_Hood](https://avatars.discourse-cdn.com/v4/letter/b/8c91f0/32.png) [@Ben\_Hood](https://forum.ansible.com/u/Ben_Hood)\ **Post date:** [November 22, 2012, 11:26pm UTC](https://forum.ansible.com/t/idempotent-unpacking/11953/8 "2012-11-22T23:26:18Z")
> Are you wanting to extract each tarball depending on whether or not that > particular one has changed, or do you want to run it if any of them change? The former. > The former would likely be best implemented using a task include file > containing your get\_url and unpacking command, and using with\_items on the > include, e.g. > tasks: > - include: fetch-extract.yml url=$s3/$item name=$item >    with\_items: >    - $tarball1 >    - $tarball2 > and in fetch-extract.yml: > - name: fetch file >    action: get\_url url=$url dest=/opt/$name >    register: fetch\_result > - name: extract file >    action: command tar -xzf /opt/$name >    when\_boolean: ${fetch\_result.changed} OK, I'll give that a go - thanks for the heads up. BTW how does the register action populate the ${fetch\_result.changed} flag? Does the get\_url command save a checksum of the last downloaded file? Cheers, Ben ---
**Author:** ![Michael\_DeHaan](https://avatars.discourse-cdn.com/v4/letter/m/c4cdca/32.png) [@Michael\_DeHaan](https://forum.ansible.com/u/Michael_DeHaan)\ **Post date:** [November 23, 2012, 1:33am UTC](https://forum.ansible.com/t/idempotent-unpacking/11953/9 "2012-11-23T01:33:16Z")
I can't remember how all the stuff I wrote works 🙂 Good. -- Michael