Hi Ruchika,

 So candidate in B.tech final year are allowed to appear for GATE exam,so you can surely appear for it but sadly date to fill form of GATE 2019 is over now.

companies recruiting through GATE for civil engineering branch varies on yearly basis but some PSU's like: ONGC, NTPC, BARC, DDA, EIL,RITES,DMRC, NBCC, Indian Oil, HPCL recruit constantly through GATE examaination.

There are state level exam as well like Madhya Pradesh Jal board which recruited recently purely based on GATE exam.

As I told before DMRC, Rites (deals in designing of rapid metro bridges etc.) also recruit through GATE exam. There is RRB exam, specially conducted by railway for different post.

I hope this was useful, please feel free to post any further queries as well.