# ansible.builtin.replace
Replace all instances of a particular string in a file using a back-referenced regular expression.

## Parameter
| Parameter      | Type              | Default | Description                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
| -------------- | ----------------- | ------- |   |
| **after**      | string            | -       | If specified, only content after this match will be replaced/removed.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
| **before**     | string            | -       | If specified, only content before this match will be replaced/removed.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
| **path**       | path / required   | -       | The file to modify.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
| **regexp**     | string / required | -       | The regular expression to look for in the contents of the file.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
| **replace**    | string            | ""      | The string to replace regexp matches.  May contain backreferences that will get expanded with the regexp capture groups if the regexp matches.  If not set, matches are removed entirely.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
| **attributes** | string            | -       | The attributes the resulting filesystem object should have. To get supported flags look at the man page for [chattr](../../../applications/cli/system/chattr.md) on the target system. The = operator is assumed as default, otherwise + or - operators need to be included in the string.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
| **backup**     | boolean           | false   | Create a backup file including the timestamp information so you can get the original file back if you somehow clobbered it incorrectly.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| **follow**     | boolean           | false   | This flag indicates that filesystem links in the destination, if they exist, should be followed.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| **force**      | boolean           | true    | Influence whether the remote file must always be replaced. If `true`, the remote file will be replaced when contents are different than the source. If `false`, the file will only be transferred if the destination does not exist.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               | 
| **group**      | string            | -       | Name of the group that should own the filesystem object, as would be fed to chown.  When left unspecified, it uses the current group of the current user unless you are root, in which case it can preserve the previous ownership.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
| **mode**       | any               | -       | The permissions the resulting filesystem object should have. For those used to _/usr/bin/chmod_ remember that modes are actually octal numbers. You must give Ansible enough information to parse them correctly. For consistent results, quote octal numbers (for example, `'644'` or `'1777'`) so Ansible receives a string and can do its own conversion from string into number. Adding a leading zero (for example, `0755`) works sometimes, but can fail in loops and some other circumstances. Giving Ansible a number without following either of these rules will end up with a decimal number which will have unexpected results. As of Ansible 1.8, the mode may be specified as a symbolic mode (for example, `u+rwx` or `u=rw,g=r,o=r`). If `mode` is not specified and the destination filesystem object **does not** exist, the default `umask` on the system will be used when setting the mode for the newly created filesystem object. If `mode` is not specified and the destination filesystem object **does** exist, the mode of the existing filesystem object will be used. |
| **owner**      | string            | -       | Name of the user that should own the filesystem object, as would be fed to chown.  When left unspecified, it uses the current user unless you are root, in which case it can preserve the previous ownership.  Specifying a numeric username will be assumed to be a user ID and not a username. Avoid numeric usernames to avoid this confusion.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
| **validate**   | string            | -       | The validation command to run before copying the updated file into the final destination.  A temporary file path is used to validate, passed in through ‘%s’ which must be present as in the examples below.  Also, the command is passed securely so [shell](../../../applications/cli/Shell.md) features such as expansion and pipes will not work.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |

## Examples
```yaml
- name: Replace old hostname with new hostname (requires Ansible >= 2.4)
  ansible.builtin.replace:
    path: /etc/hosts
    regexp: '(\s+)old\.host\.name(\s+.*)?$'
    replace: '\1new.host.name\2'

- name: Replace after the expression till the end of the file (requires Ansible >= 2.4)
  ansible.builtin.replace:
    path: /etc/apache2/sites-available/default.conf
    after: 'NameVirtualHost [*]'
    regexp: '^(.+)$'
    replace: '# \1'

- name: Replace before the expression till the begin of the file (requires Ansible >= 2.4)
  ansible.builtin.replace:
    path: /etc/apache2/sites-available/default.conf
    before: '# live site config'
    regexp: '^(.+)$'
    replace: '# \1'

# Prior to Ansible 2.7.10, using before and after in combination did the opposite of what was intended.
# see https://github.com/ansible/ansible/issues/31354 for details.
- name: Replace between the expressions (requires Ansible >= 2.4)
  ansible.builtin.replace:
    path: /etc/hosts
    after: '<VirtualHost [*]>'
    before: '</VirtualHost>'
    regexp: '^(.+)$'
    replace: '# \1'

- name: Supports common file attributes
  ansible.builtin.replace:
    path: /home/jdoe/.ssh/known_hosts
    regexp: '^old\.host\.name[^\n]*\n'
    owner: jdoe
    group: jdoe
    mode: '0644'

- name: Supports a validate command
  ansible.builtin.replace:
    path: /etc/apache/ports
    regexp: '^(NameVirtualHost|Listen)\s+80\s*$'
    replace: '\1 127.0.0.1:8080'
    validate: '/usr/sbin/apache2ctl -f %s -t'

- name: Short form task (in ansible 2+) necessitates backslash-escaped sequences
  ansible.builtin.replace: path=/etc/hosts regexp='\\b(localhost)(\\d*)\\b' replace='\\1\\2.localdomain\\2 \\1\\2'

- name: Long form task does not
  ansible.builtin.replace:
    path: /etc/hosts
    regexp: '\b(localhost)(\d*)\b'
    replace: '\1\2.localdomain\2 \1\2'

- name: Explicitly specifying positional matched groups in replacement
  ansible.builtin.replace:
    path: /etc/ssh/sshd_config
    regexp: '^(ListenAddress[ ]+)[^\n]+$'
    replace: '\g<1>0.0.0.0'

- name: Explicitly specifying named matched groups
  ansible.builtin.replace:
    path: /etc/ssh/sshd_config
    regexp: '^(?P<dctv>ListenAddress[ ]+)(?P<host>[^\n]+)$'
    replace: '#\g<dctv>\g<host>\n\g<dctv>0.0.0.0'
```