Suppose I have two files like below and i would like to substract the values from two files:-

File 1 -

```
emcas_bdl_migrate=2
emcas_biaas_dev=691
emcas_brs_ba=462
emcas_cc_analytics=1985
emcas_clm_reporting=0
emcas_collab_xsat=3659
emcas_cpsd_cee=10
emcas_cpsd_hcp=0
emcas_e2ep_ba=81
emcas_edservices_bi=643

```

And File 2 -

```
emcas_bdl_migrate=2
emcas_biaas_dev=63
emcas_brs_ba=430
emcas_cc_analytics=2148
emcas_clm_reporting=16
emcas_collab_xsat=4082
emcas_cpsd_cee=11
emcas_cpsd_hcp=0
emcas_cs_logistics=0
emcas_e2ep_ba=195
emcas_edservices_bi=1059

```

There can be extra values for File 2 (eg. `emcas_cs_logistics=0` in 2nd file extra). Which will be merged in the final output file.

Want a desired output as File 3 -

```
emcas_bdl_migrate=0
emcas_biaas_dev=-628
emcas_brs_ba=-32
emcas_cc_analytics=163
emcas_clm_reporting=16
emcas_collab_xsat=423
emcas_cpsd_cee=11
emcas_cpsd_hcp=0
emcas_cs_logistics=0
emcas_e2ep_ba=-114
emcas_edservices_bi=416

```