I like either for grep'ing

There are times when you want to grep for multiple different lines from a file. For example, the text file below could be an example of a log file and I'd like to see all the CmdStat entries I had and what Value line followed each of them.

log.txt:
CmdStat=InFlow
Info=More Data and Values
CmdStat=OutStat
Value=-3
CmdStat=Done
Value=42
Notes=end

Well, the first guess of running "grep CmdStat log.txt" followed by "grep Value log.txt" will certainly generate all the right lines, but it will not tell me the where the Value lines are compare to the CmdStat lines. There could be CmdStat lines without Value lines and vice versa.

The correct solution is to use the very useful -e (either) option. Doing a "grep -eCmdStat= -eValue= log.txt" will yield:
CmdStat=InFlow
CmdStat=OutStat
Value=-3
CmdStat=Done
Value=42

which shows me all the CmdStat and Value entries. Note that I used Value= instead of Value so we do not accidentally get lines with the word Value. Always a good idea to grep for a word as unique as possible.

You may of course also combine -e with other useful options, such as -i (case insensitive) and -v (except). So if I want to weed out all the Info and Notes lines from the file, I could do a "grep -v -eNotes= -eInfo= log.txt"

Nifty.