UNIX Desktop Questions & Answers

Originally Posted by pseudocoder

Maybe this excerpt from the egrep man page will help you to better understand how egrep works, note the sentence that I have underlined:

DESCRIPTION
grep searches the named input FILEs (or standard input if no files are
named, or the file name - is given) for lines containing a match to the
given PATTERN. By default, grep prints the matching lines.


---------- Post updated at 00:54 ---------- Previous update was at 00:50 ----------

Code:

$ egrep '(Jolly)|(Brewers)' public
Jolly Brewers
$ egrep -o '(Jolly)|(Brewers)' public
Jolly
Brewers
$

Originally Posted by pseudocoder

egrep '(Jolly)|(Brewers)' public

In fact in this case the pipe means AND as well as OR.
AFAIK it has nothing to do with the brackets, if you omit the brackets, the result should be the same.
Additionally note the difference between one pipe and two pipes, where the latter means OR in shell.

---------- Post updated at 01:32 ---------- Previous update was at 01:22 ----------

All right, I have to correct myself, one pipe does indeed mean OR
Regular Expression Tutorial (Section "Alternation")

Originally Posted by pseudocoder

Strange, after some more research, it looks like I initially was right with AND/OR... Finally I'll stick by my initial definition.

A pipe in the egrep pattern stands for a delimiter. A double pipe stands for OR.
However egrep will in both cases print the matching line (which contains both patterns).
Let me illustrate this:

Code:

$ egrep --color=always '(Jolly)|(Brewers)' public
Jolly Brewers
$ egrep --color=always '(Jolly)||(Brewers)' public
Jolly Brewers
$

--colour[=WHEN], --color[=WHEN]
Surround the matching string with the marker find in GREP_COLOR
environment variable. WHEN may be `never', `always', or `auto'