The command line program grep recognizes matching patterns.
An example what grep can do is shown through the following line.
In the line, the -e flag tells the program to search for patterns starting
with special characters, the \| (which is a pipe…
more on that later) allows multiple things to be found (essentially an “or”
feature), and the > directs the output to a new file.
The whole slew of what you’re looking for should be in open quotes.
$ grep -e '^ATOM\|^HETATM\|^TER\|^END' 1A31_cleanup_o.pdb > 1A31_cleanup_o2.pdb
If you used something like
$ grep 'word*' *.txt
then all of the matching lines starting with “word” found in text files would be printed to the Terminal.