# Ansible - Advanced shell command execution syntax **URL:** \ **Category:** Ansible Project\ **Created:** [August 22, 2014, 4:47am UTC](https://forum.ansible.com/t/ansible-advanced-shell-command-execution-syntax/16006 "2014-08-22T04:47:59Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![Imran\_Khan1](https://avatars.discourse-cdn.com/v4/letter/i/a4c791/32.png) [@Imran\_Khan1](https://forum.ansible.com/u/Imran_Khan1)\ **Post date:** [August 22, 2014, 4:47am UTC](https://forum.ansible.com/t/ansible-advanced-shell-command-execution-syntax/16006/1 "2014-08-22T04:47:59Z")
I have 3 variables named IPOctet, ServerIPRange and epcrange. If I perform the following operation in my terminal, it works perfectly ```auto IPOctet=$(echo "$ServerIPRange/$epcrange+$IPOctet" | bc) ``` How to I do something similar in a ansible inside a task, for e.g ```auto --- - hosts: localhost gather_facts: False vars_prompt: - name: epcrange prompt: Enter the number of EPCs that you want to configure private: False default: "1" - name: serverrange prompt: Enter the number of Cleints that you want to configure private: False defualt: "1" - name: ServerIPRange prompt: Enter the ServerIP range private: False default: '128' - name: LastIPOctet prompt: Enter The last Octet of the IP you just entered private: False default: '10' pre_tasks: - name: Set some facts set_fact: ServerIP1: "{{ServerIP}}" ServerIPRange1: "{{ServerIPRange}}" IPOctet: "{{LastIPOctet}}" - name: local action math local_action: shell {{IPOctet}}=$(echo "${{ServerIPRange}}/${{epcrange}}+${{IPOctet}}" | bc) # Proper Syntax? with_sequence: start=1 end=4 register: result ignore_errors: yes ``` What is the proper syntax for this command? Maybe using shell echo “…” . I just need to save the contents of this command into the IPOctet variable and IPOctet will change with each loop iteration and the results should be stored in my result register P.S: how can I access the individual items in the array sepearately? ---
**Author:** ![Henry\_Finucane](https://avatars.discourse-cdn.com/v4/letter/h/94ad74/32.png) [@Henry\_Finucane](https://forum.ansible.com/u/Henry_Finucane)\ **Post date:** [August 22, 2014, 5:40am UTC](https://forum.ansible.com/t/ansible-advanced-shell-command-execution-syntax/16006/2 "2014-08-22T05:40:27Z")
As an aside, you can do math in Jinja2- - name: bashless math   set\_fact:     IPOctet: "{{ 4\*(ServerIPRange/epcrange)+IPOctet }}" will do something approaching what you want. If you want to get the actual shell-out working, something like this is going to be enlightening:   - name: local action math     local\_action: shell echo "{{ServerIPRange}}/{{epcrange}}+{{IPOctet}}" | bc     with\_sequence: start=1 end=4     register: result   - debug: var=result "debug: var=result" will dump a pretty-printed JSON structure, so you'll know what's available, and what you can use. You should try it with & without the with\_sequence. ---
**Author:** ![Imran\_Khan1](https://avatars.discourse-cdn.com/v4/letter/i/a4c791/32.png) [@Imran\_Khan1](https://forum.ansible.com/u/Imran_Khan1)\ **Post date:** [August 22, 2014, 6:17am UTC](https://forum.ansible.com/t/ansible-advanced-shell-command-execution-syntax/16006/3 "2014-08-22T06:17:25Z")
Thank you for your quick reply: But this works, but not in a loop! - name: bashless math set\_fact: IPOctet: “{{ (ServerIPRange|int/epcrange|int)+IPOctet|int }}” with\_sequence: start=1 end=4 register: IPOctet this wont work either: - name: bashless math set\_fact: IPOctet: “{{ (ServerIPRange|int/epcrange|int)+IPOctet|int }}” register: IPOctet with\_sequence: start=1 end=4 register: my\_ip\_octet I need to save the value in IPOctet repetitively ---
**Author:** ![Imran\_Khan1](https://avatars.discourse-cdn.com/v4/letter/i/a4c791/32.png) [@Imran\_Khan1](https://forum.ansible.com/u/Imran_Khan1)\ **Post date:** [August 22, 2014, 6:19am UTC](https://forum.ansible.com/t/ansible-advanced-shell-command-execution-syntax/16006/4 "2014-08-22T06:19:21Z")
Again this will save the same value 4 times! - name: local action math local\_action: shell echo “{{ServerIPRange}}/{{epcrange}}+{{IPOctet}}” | bc with\_sequence: start=1 end=4 register: result - debug: var=resu ---
**Author:** ![Michael\_DeHaan1](https://avatars.discourse-cdn.com/v4/letter/m/5e9695/32.png) [@Michael\_DeHaan1](https://forum.ansible.com/u/Michael_DeHaan1)\ **Post date:** [August 22, 2014, 11:24am UTC](https://forum.ansible.com/t/ansible-advanced-shell-command-execution-syntax/16006/5 "2014-08-22T11:24:13Z")
There’s a bugfix PR for that which I need to test. You can of course still do this as a shell command too, right now. What problem are you having at the shell? ---
**Author:** ![Imran\_Khan1](https://avatars.discourse-cdn.com/v4/letter/i/a4c791/32.png) [@Imran\_Khan1](https://forum.ansible.com/u/Imran_Khan1)\ **Post date:** [August 22, 2014, 12:05pm UTC](https://forum.ansible.com/t/ansible-advanced-shell-command-execution-syntax/16006/6 "2014-08-22T12:05:33Z")
The shell command only does the calculation once and stores the same value in each loop iteration. I want it to run the command by using the last calculated value, which is supposedly not happening for me. Can the jinj2 sum or replace filters be of any help ? ---
**Author:** ![Michael\_DeHaan1](https://avatars.discourse-cdn.com/v4/letter/m/5e9695/32.png) [@Michael\_DeHaan1](https://forum.ansible.com/u/Michael_DeHaan1)\ **Post date:** [August 22, 2014, 12:06pm UTC](https://forum.ansible.com/t/ansible-advanced-shell-command-execution-syntax/16006/7 "2014-08-22T12:06:04Z")
I’m not understanding what “run the command using the last calculated value” means, unfortunately. ---
**Author:** ![Imran\_Khan1](https://avatars.discourse-cdn.com/v4/letter/i/a4c791/32.png) [@Imran\_Khan1](https://forum.ansible.com/u/Imran_Khan1)\ **Post date:** [August 22, 2014, 12:44pm UTC](https://forum.ansible.com/t/ansible-advanced-shell-command-execution-syntax/16006/8 "2014-08-22T12:44:10Z")
> Well I just want a loop, that does the following: IPOctet=$(echo “$ServerIPRange/$epcrange+$IPOctet” | bc) as you can see IPOctet is added to $ServerIPRange/$epcrange and the result is SAVED in IPOctet In each loop IPOctet is is say incremented by “x” and the result is saved in IPOctet again What happens: The loop runs the number of times but saves the same value in each loop iteration. eg: IPOctet=“5” ServerIPRange=“16” epcrange=“2” IPOctet= 5 + 16/2 = 13 In the next iteration the result should be IPOctet= 13 + 8 = 21 //But what happens is that IPOctet stays constant at “13” In the third iteration the result should be IPOctet= 21 + 8 = 29 //IPOctet is doesn’t change, reamins 13 and will remain 13 no matter how many iterations of the loop are run I hope I have got my point across. Now any suggestions on the solution ? ---
**Author:** ![Henry\_Finucane](https://avatars.discourse-cdn.com/v4/letter/h/94ad74/32.png) [@Henry\_Finucane](https://forum.ansible.com/u/Henry_Finucane)\ **Post date:** [August 22, 2014, 5:27pm UTC](https://forum.ansible.com/t/ansible-advanced-shell-command-execution-syntax/16006/9 "2014-08-22T17:27:17Z")
> Thank you for your quick reply: > But this works, but not in a loop! > >     - name: bashless math >       set\_fact: >         IPOctet: "{{ (ServerIPRange|int/epcrange|int)+IPOctet|int }}" >       with\_sequence: start=1 end=4 >       register: IPOctet You may have missed a crucial bit of what I wrote- your algorithm doesn't actually require any iteration. It decomposes into IPrange/epcrange + (IPrange/epcrange + (IPrange/epcrange + (IPrange/epcrange + LastIPOctet) ) ) which is the same thing as 4 \* (IPrange/epcrange) + LastIPOctet ---
**Author:** ![Imran\_Khan1](https://avatars.discourse-cdn.com/v4/letter/i/a4c791/32.png) [@Imran\_Khan1](https://forum.ansible.com/u/Imran_Khan1)\ **Post date:** [August 23, 2014, 5:09pm UTC](https://forum.ansible.com/t/ansible-advanced-shell-command-execution-syntax/16006/10 "2014-08-23T17:09:26Z")
I posted that code piece of code for explanation purposes only, loop iteration i.e. the stop value is not fixed and will vary each time depending on user input (it is taken from the user at run time using vars\_prompt) Please can you tell me how to do x=x+y with x=10(will change with each loop iteration) and y=5 (remains constant), inside a loop that runs ten any number of time ---
**Author:** ![sivel](https://sea1.discourse-cdn.com/ansible/user_avatar/forum.ansible.com/sivel/32/1198_2.png) [@sivel](https://forum.ansible.com/u/sivel)\ **Post date:** [August 23, 2014, 7:32pm UTC](https://forum.ansible.com/t/ansible-advanced-shell-command-execution-syntax/16006/11 "2014-08-23T19:32:43Z")
Isn’t what you are doing mathematically equivalent to: z = x + (y \* iterations) In which case, why do you need to store each result? Why not just run the task where you want to use this value using with\_sequence, and use this formula directly? Such as this contrived example: - debug: msg=“{{ IPOctet + (ServerIPRange//epcrange) \* item|int }}” with\_sequence: count=“{{ iterations }}” ---
**Author:** ![Henry\_Finucane](https://avatars.discourse-cdn.com/v4/letter/h/94ad74/32.png) [@Henry\_Finucane](https://forum.ansible.com/u/Henry_Finucane)\ **Post date:** [August 23, 2014, 8:23pm UTC](https://forum.ansible.com/t/ansible-advanced-shell-command-execution-syntax/16006/12 "2014-08-23T20:23:07Z")
> I posted that code piece of code for explanation purposes only, loop iteration i.e. the stop value is not fixed and will vary each time depending on user input (it is taken from the user at run time using vars\_prompt) > > Please can you tell me how to do x=x+y with x=10(will change with each loop iteration) and y=5 (remains constant), inside a loop that runs ten any number of time That decomposes the same way! In any case, the yaml/jinja2 layer is generally the wrong layer to do logic in if your logic is going to get complicated. If you write a module, you can do anything python can do. ---
**Author:** ![Imran\_Khan1](https://avatars.discourse-cdn.com/v4/letter/i/a4c791/32.png) [@Imran\_Khan1](https://forum.ansible.com/u/Imran_Khan1)\ **Post date:** [August 24, 2014, 8:52am UTC](https://forum.ansible.com/t/ansible-advanced-shell-command-execution-syntax/16006/13 "2014-08-24T08:52:16Z")
Nope, I can’t use them like that, my playbook is very complex, with some tasks running on some hosts serially