I am trying to use grep with a regex to find lines in a file that match 1 of 2 possible strings. Here is my grep:$ grep ^ID.*(ETS|FBS) my_file.txtThe above grep returns no results. However if I execute either:$ grep ^ID.*ETS my_file.txt  or   $ grep ^ID.*FBS my_file.txt  I do match specific lines. Why is my OR regex not matching? Thanks in advance for the help!
Grep 'OR' regex problem
grep;regular expression
With normal regex, the characters (, | and ) need to be escaped. So you should use$ grep ^ID.*\(ETS\|FBS\) my_file.txtYou don't need the escapes when you use the extended regex (-E)option. See man grep, section Basic vs Extended Regular Expressions.