Using if/else statement to run a command in shell

Question

I wanted to run a command in shell (basically via ansible playbook), the condition is, if the ps status gives non zero exit code then it needs to run another command. I don't wanted to split this into two tasks, one to check the ps status and another to execute the command. Instead using if/else condition, can this be merged into a single task?

ps -ef | grep -v grep | grep httpd

If the above command exits with non zero status, then I need to fire another command which is given below. How can I merge these two commands as one and include this as a single task?

nohup /root/scripts/httpd.sh start &

Answer 1

Solution

This does what you want:

  tasks:
    - name: pser
      shell: ps -ef | grep [h]ttpd && echo found || nohup sleep 1000 &

NOTE: I'm using the command sleep 1000 as a stand-in for your Apache daemon process, httpd.

Example Run

$ cat pb.yml
- name: Hello Ansible - quick start
  hosts: all
  connection: local

  tasks:
    - name: pser
      shell: ps -ef | grep [h]ttpd && echo found || nohup sleep 1000 &

Notice we have neither a sleep or httpd process present:

$ ps -eaf|grep -E "[s]leep|[h]ttpd"
$

Now we run the playbook:

$ ansible-playbook -i inventory pb.yml

PLAY [Hello Ansible - quick start] *************************************************************************************************************************************************************************************************

TASK [Gathering Facts] *************************************************************************************************************************************************************************************************************
ok: [localhost]

TASK [pser] ************************************************************************************************************************************************************************************************************************
changed: [localhost]

PLAY RECAP *************************************************************************************************************************************************************************************************************************
localhost                  : ok=2    changed=1    unreachable=0    failed=0

Now we have a sleep process going:

$ ps -eaf|grep -E "[s]leep|[h]ttpd"
  501 34422     1   0  2:00AM ttys000    0:00.00 /bin/bash -c ps -ef | grep [h]ttpd && echo found || nohup sleep 1000 &
  501 34425 34422   0  2:00AM ttys000    0:00.00 sleep 1000

Now if we reset things and do the same thing but this time open up a edit window with a filename of httpd to "fake out" the grep [h]ttpd:

$ ps -eaf|grep -E "[s]leep|[h]ttpd"
  501 34542     1   0  2:02AM ??         0:00.27 /usr/local/Cellar/macvim/HEAD-4e631a0/MacVim.app/Contents/bin/../MacOS/Vim -f -g httpd

Running the playbook this time will do nothing:

$ ansible-playbook -i inventory pb.yml

PLAY [Hello Ansible - quick start] *************************************************************************************************************************************************************************************************

TASK [Gathering Facts] *************************************************************************************************************************************************************************************************************
ok: [localhost]

TASK [pser] ************************************************************************************************************************************************************************************************************************
changed: [localhost]

PLAY RECAP *************************************************************************************************************************************************************************************************************************
localhost                  : ok=2    changed=1    unreachable=0    failed=0

Still just our edit window with the 'httpd' file open:

$ ps -eaf|grep -E "[s]leep|[h]ttpd"
  501 34542     1   0  2:02AM ??         0:00.27 /usr/local/Cellar/macvim/HEAD-4e631a0/MacVim.app/Contents/bin/../MacOS/Vim -f -g httpd