From grep's manual
‘-e pattern’ ‘--regexp=pattern’
This can be used to specify multiple search patterns, or to protect a pattern beginning with a ‘-’. (‘-e’ is specifi ed by POSIX.)
What does "specify multiple search patterns" mean?
Does it mean exactly to output each line which contains all the search patterns specified by
-e? If yes, does it do the same thing as piping multiple greps, each of which matches one of the patterns?