adduser.sh

#!/bin/bash

FILE=$1
USER=$2
EMAIL=$3

realfile=$(readlink -f $FILE)

cat << EOF | augtool -Ast "Xml incl ${realfile}"
# Remove #empty node
clear /files${realfile}/users

defnode user /files${realfile}/users/user[username/#text = "${USER}"]
set \$user/username/#text "${USER}"
set \$user/email/#text "${EMAIL}"
EOF

empty.xml

<users />

fill_empty.augtool

$ augtool -r . -At "Xml incl /empty.xml"
augtool> clear /files/empty.xml/users
users
augtool> clear /files/empty.xml/users
augtool> set /files/empty.xml/users/user/username/#text "blah"
augtool> set /files/empty.xml/users/user/email/#text "blah@example.com"
augtool> print /files/empty.xml/
/files/empty.xml
/files/empty.xml/users
/files/empty.xml/users/user
/files/empty.xml/users/user/username
/files/empty.xml/users/user/username/#text = "blah"
/files/empty.xml/users/user/email
/files/empty.xml/users/user/email/#text = "blah@example.com"
augtool> save
Saved 1 file(s)

$ git diff empty.xml
diff --git a/empty.xml b/empty.xml
index 8909974..9979def 100644
--- a/empty.xml
+++ b/empty.xml
@@ -1 +1,4 @@
-<users />
\ No newline at end of file
+<users><user><username>blah</username>
+<email>blah@example.com</email>
+</user>
+</users>

fill_empty_moar.augtool

$  augtool -r . -At "Xml incl /empty.xml"
augtool> defnode foo /files/empty.xml/users/user[username/#text = "foo"]
augtool> set $foo/username/#text "foo"
augtool> set $foo/email/#text "foo@example.com"
augtool> save
Saved 1 file(s)

$ git diff empty.xml
diff --git a/empty.xml b/empty.xml
index 8909974..8fd2881 100644
--- a/empty.xml
+++ b/empty.xml
@@ -1 +1,7 @@
-<users />
\ No newline at end of file
+<users><user><username>blah</username>
+<email>blah@example.com</email>
+</user>
+<user><username>foo</username>
+<email>foo@example.com</email>
+</user>
+</users>

parse_empty.augtool

$  augtool -r . -At "Xml incl /empty.xml"
augtool> print /files/empty.xml
/files/home/rpinson/bas/augeas/empty.xml
/files/home/rpinson/bas/augeas/empty.xml/users = "#empty"

parse_users.augtool

$ augtool -r . -At "Xml incl /users.xml"
augtool> print /files//users.xml
/files/users.xml
/files/users.xml/users
/files/users.xml/users/#text = "\n  "
/files/users.xml/users/user
/files/users.xml/users/user/#text[1] = "\n    "
/files/users.xml/users/user/username
/files/users.xml/users/user/username/#text = "blah"
/files/users.xml/users/user/#text[2] = "    "
/files/users.xml/users/user/email
/files/users.xml/users/user/email/#text = "blah@example.com"
/files/users.xml/users/user/#text[3] = "  "

users.xml

<users>
  <user>
    <username>blah</username>
    <email>blah@example.com</email>
  </user>
</users>

xml_user.pp

define xml_user (
  $file,
  $user,
  $email,
  $ensure = 'present',
) {

  case $ensure {
    'present': {
      $changes = [
        "clear users",
        "defnode user users/user[username/#text = '${user}'] ''",
        "set \$user/username/#text '${user}'",
        "set \$user/email/#text '${email}'",
      ]

    }

    'absent': {
      $changes = "rm users/user[username/#text = '${user}']"
    }

    default: {
      fail("Unknown value for \$ensure '${ensure}'")
    }
  }


  augeas { "manage user ${user} in ${file}":
    lens    => 'Xml.lns',
    incl    => $file,
    context => "/files${file}",
    changes => $changes,
  }
}

xml_user { 'foo':
  file  => '/home/rpinson/bas/augeas/d34795066930bcd46d1000cd7a0ecf02/empty.xml',
  user  => 'foo',
  email => 'foo@example.com',
}