How do I filter a GFF file by gene type?
grep -E 'gene_type "(processed_pseudogene|lincRNA|unprocessed_pseudogene|antisense_RNA)";' input_file.txt


Explanation


grep -E: use extended regular expression so you don't need to escape things.
This kind of expression (foo|bar|baz) allows grep to include either of these strings. Hence, the total expression will match gene_type "processed_pseudogene";', gene_type "lincRNA";', etc.