Ansible: insert string at the end of the line but only if string is not present OR/AND change value if present

Question

I am struggling below scenario:

In /etc/default/grub file, there is GRUB_CMDLINE_LINUX_DEFAULT stanza, I need to insert audit=1 at the end of the line if value is not there already (note that there is quote char at the end of line) . If audit=0 is present change it to audit=1 .

lineinfile ansible module does not work, especially with inserting before last quote (").

Original /etc/default/grub:

GRUB_TIMEOUT=5
GRUB_DEFAULT=saved
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT="rootfstype=xfs quiet splash acpi_osi="

Optional /etc/default/grub:

GRUB_TIMEOUT=5
GRUB_DEFAULT=saved
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT="rootfstype=xfs quiet splash acpi_osi= audit=0" # change audit=0 to audit=1
#OR:
#GRUB_CMDLINE_LINUX_DEFAULT="rootfstype=xfs quiet splash acpi_osi= audit=1" # audit=1 is already here, so no action needed

Desired /etc/default/grub:

GRUB_TIMEOUT=5
GRUB_DEFAULT=saved
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT="rootfstype=xfs quiet splash acpi_osi= audit=1"

Answer 1

I created a file where the text is audit=0 and tried to replace it with audit=1

my file was: grubfile:

GRUB_TIMEOUT=5
GRUB_DEFAULT=saved
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT="rootfstype=xfs quiet splash acpi_osi= audit=0"

my playbook:

---
  - name: read grub file
    lineinfile:
      dest: /home/myhome/grubfile.txt
      regexp: '^(.*)audit=0(.*)$'
      line: '\1audit=1\2'
      backup: yes
      backrefs: yes

Basically we play with regexp taking the audit=1 as the regexp and storing the rest of the string with backrefs the resulting file is:

GRUB_TIMEOUT=5
GRUB_DEFAULT=saved
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT="rootfstype=xfs quiet splash acpi_osi= audit=1"

Edit: This code will add it even if doesn't exist, It will first modify if the audit=0 is present, then will check if audit=1 exists and if it doesn't exist will append the audit=1 to the beginning of the quotes:

---
  - name:
    lineinfile:
      dest: /home/mypath/grubfile.txt
      regexp: '^(.*)audit=1(.*)$'
      state: absent
    check_mode: yes
    changed_when: false
    register: auditexist
  - name: if audit=0 write audit=1
    lineinfile:
      dest: /home/mypath/grubfile.txt
      regexp: '^(.*)audit=0(.*)$'
      line: '\1audit=1\2'
      backup: yes
      backrefs: yes
    register: auditmodified
  - name: appen
    lineinfile:
     dest: /home/ivan/grubfile.txt
     regexp: '^(.*)GRUB_CMDLINE_LINUX_DEFAULT="(.*)$'
     line: '\1GRUB_CMDLINE_LINUX_DEFAULT="audit=1 \2 '
     backup: yes
     backrefs: yes
    when: not auditexist.found and not auditmodified.changed

result:

GRUB_TIMEOUT=5
GRUB_DEFAULT=saved
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT="audit=1 rootfstype=xfs quiet splash acpi_osi="