egrep "foo|bar" *.txt
veya
grep "foo\|bar" *.txt
grep -E "foo|bar" *.txt
gnu-grep’in man sayfasını seçici olarak göstererek:
-E, --extended-regexp
Interpret PATTERN as an extended regular expression (ERE, see below). (-E is specified by POSIX.)
Matching Control
-e PATTERN, --regexp=PATTERN
Use PATTERN as the pattern. This can be used to specify multiple search patterns, or to protect a pattern
beginning with a hyphen (-). (-e is specified by POSIX.)
(...)
grep understands two different versions of regular expression syntax: “basic” and “extended.” In GNU grep, there
is no difference in available functionality using either syntax. In other implementations, basic regular
expressions are less powerful. The following description applies to extended regular expressions; differences for
basic regular expressions are summarized afterwards.
Başlangıçta daha fazla okumadım, bu yüzden ince farklılıkları tanımadım:
Basic vs Extended Regular Expressions
In basic regular expressions the meta-characters ?, +, {, |, (, and ) lose their special meaning; instead use the
backslashed versions \?, \+, \{, \|, \(, and \).
Her zaman egrep ve gereksiz yere parens kullandım, çünkü örneklerden öğrendim. Şimdi yeni bir şey öğrendim. :)