how to edit XML using bash script?

Question

1
2

Need to change values 1 and 2 from bash

Answer 1

To change tag's value to 2 and tag1's value to 3, using XMLStarlet:

xmlstarlet ed \
  -u '/root/tag' -v 2 \
  -u '/root/tag1' -v 3 \
  new.xml

---

Using your sample input:

xmlstarlet ed \
  -u '/root/tag' -v 2 \
  -u '/root/tag1' -v 3 \
  <<<'12'

...emits as output:

  2
  3